So I made a model to render on the player but im confused on how to make it so when the player put the armor on that it renders on the player? 
Model Class:

Spoiler

package com.derpz.nukaisl.client.models;// Made with Blockbench 4.3.1
// Exported for Minecraft version 1.17 - 1.18 with Mojang mappings
// Paste this class into your mod and generate all required imports


import com.derpz.nukaisl.FalloutMod;
import com.mojang.blaze3d.vertex.PoseStack;
import com.mojang.blaze3d.vertex.VertexConsumer;
import net.minecraft.client.model.EntityModel;
import net.minecraft.client.model.geom.ModelLayerLocation;
import net.minecraft.client.model.geom.ModelPart;
import net.minecraft.client.model.geom.PartPose;
import net.minecraft.client.model.geom.builders.*;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.world.entity.Entity;

public class UnderArmorModel<T extends Entity> extends EntityModel<T> {
	// This layer location should be baked with EntityRendererProvider.Context in the entity renderer and passed into this model's constructor
	public static final ModelLayerLocation LAYER_LOCATION = new ModelLayerLocation(new ResourceLocation(FalloutMod.MOD_ID, "underarmormodel"), "main");
	public final ModelPart Head;
	public final ModelPart Body;
	public final ModelPart RightArm;
	public final ModelPart LeftArm;
	public final ModelPart RightLeg;
	public final ModelPart LeftLeg;

	public UnderArmorModel(ModelPart root) {
		this.Head = root.getChild("Head");
		this.Body = root.getChild("Body");
		this.RightArm = root.getChild("RightArm");
		this.LeftArm = root.getChild("LeftArm");
		this.RightLeg = root.getChild("RightLeg");
		this.LeftLeg = root.getChild("LeftLeg");
	}

	public UnderArmorModel(ModelPart head, ModelPart body, ModelPart rightArm, ModelPart leftArm, ModelPart rightLeg, ModelPart leftLeg) {
		Head = head;
		Body = body;
		RightArm = rightArm;
		LeftArm = leftArm;
		RightLeg = rightLeg;
		LeftLeg = leftLeg;
	}

	public static LayerDefinition createBodyLayer() {
		MeshDefinition meshdefinition = new MeshDefinition();
		PartDefinition partdefinition = meshdefinition.getRoot();

		PartDefinition Head = partdefinition.addOrReplaceChild("Head", CubeListBuilder.create().texOffs(0, 0).addBox(-4.0F, -8.0F, -4.0F, 8.0F, 8.0F, 8.0F, new CubeDeformation(0.1F))
		.texOffs(32, 0).addBox(-4.0F, -8.0F, -4.0F, 8.0F, 8.0F, 8.0F, new CubeDeformation(0.5F)), PartPose.offset(0.0F, 0.0F, 0.0F));

		PartDefinition Body = partdefinition.addOrReplaceChild("Body", CubeListBuilder.create().texOffs(16, 16).addBox(-4.0F, 0.0F, -2.0F, 8.0F, 12.0F, 4.0F, new CubeDeformation(0.1F))
		.texOffs(16, 32).addBox(-4.0F, 0.0F, -2.0F, 8.0F, 12.0F, 4.0F, new CubeDeformation(0.25F)), PartPose.offset(0.0F, 0.0F, 0.0F));

		PartDefinition RightArm = partdefinition.addOrReplaceChild("RightArm", CubeListBuilder.create().texOffs(40, 16).addBox(-3.0F, -2.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.1F))
		.texOffs(40, 32).addBox(-3.0F, -2.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.25F)), PartPose.offset(-5.0F, 2.0F, 0.0F));

		PartDefinition LeftArm = partdefinition.addOrReplaceChild("LeftArm", CubeListBuilder.create().texOffs(32, 48).addBox(-1.0F, -2.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.1F))
		.texOffs(48, 48).addBox(-1.0F, -2.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.25F)), PartPose.offset(5.0F, 2.0F, 0.0F));

		PartDefinition RightLeg = partdefinition.addOrReplaceChild("RightLeg", CubeListBuilder.create().texOffs(0, 16).addBox(-2.0F, 0.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.1F))
		.texOffs(0, 32).addBox(-2.0F, 0.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.25F)), PartPose.offset(-1.9F, 12.0F, 0.0F));

		PartDefinition LeftLeg = partdefinition.addOrReplaceChild("LeftLeg", CubeListBuilder.create().texOffs(16, 48).addBox(-2.0F, 0.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.1F))
		.texOffs(0, 48).addBox(-2.0F, 0.0F, -2.0F, 4.0F, 12.0F, 4.0F, new CubeDeformation(0.25F)), PartPose.offset(1.9F, 12.0F, 0.0F));

		return LayerDefinition.create(meshdefinition, 16, 16);
	}

	@Override
	public void setupAnim(T entity, float limbSwing, float limbSwingAmount, float ageInTicks, float netHeadYaw, float headPitch) {

	}

	@Override
	public void renderToBuffer(PoseStack poseStack, VertexConsumer vertexConsumer, int packedLight, int packedOverlay, float red, float green, float blue, float alpha) {
		Head.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
		Body.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
		RightArm.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
		LeftArm.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
		RightLeg.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
		LeftLeg.render(poseStack, vertexConsumer, packedLight, packedOverlay, red, green, blue, alpha);
	}
}

Registry Event:
 

Spoiler

@SubscribeEvent
public static void registerLayerDefinitions(EntityRenderersEvent.RegisterLayerDefinitions event) {
    event.registerLayerDefinition(UnderArmorModel.LAYER_LOCATION, UnderArmorModel::createBodyLayer);
}

 

 

Item Class:
(the initialize client method I used here was something I saw from another post I thought it was what I was missing but it still doesn't render)

package com.derpz.nukaisl.item.custom;

import com.derpz.nukaisl.client.models.UnderArmorModel;
import com.derpz.nukaisl.item.ModArmorMaterials;
import com.google.common.collect.ImmutableMap;
import net.minecraft.client.Minecraft;
import net.minecraft.client.model.HumanoidModel;
import net.minecraft.client.model.geom.ModelPart;
import net.minecraft.world.effect.MobEffectInstance;
import net.minecraft.world.effect.MobEffects;
import net.minecraft.world.entity.Entity;
import net.minecraft.world.entity.EquipmentSlot;
import net.minecraft.world.entity.LivingEntity;
import net.minecraft.world.entity.player.Player;
import net.minecraft.world.item.ArmorItem;
import net.minecraft.world.item.ArmorMaterial;
import net.minecraft.world.item.Item;
import net.minecraft.world.item.ItemStack;
import net.minecraft.world.level.Level;
import net.minecraftforge.client.extensions.common.IClientItemExtensions;
import software.bernie.geckolib3.core.IAnimatable;
import software.bernie.geckolib3.core.PlayState;
import software.bernie.geckolib3.core.builder.AnimationBuilder;
import software.bernie.geckolib3.core.controller.AnimationController;
import software.bernie.geckolib3.core.event.predicate.AnimationEvent;
import software.bernie.geckolib3.core.manager.AnimationData;
import software.bernie.geckolib3.core.manager.AnimationFactory;
import software.bernie.geckolib3.item.GeoArmorItem;

import java.util.Collections;
import java.util.Map;

public class UnderArmorItem extends ArmorItem {


    public UnderArmorItem(ArmorMaterial pMaterial, EquipmentSlot pSlot, Properties pProperties) {
        super(pMaterial, pSlot, pProperties);
    }

    @Override
    public void initializeClient(java.util.function.Consumer<net.minecraftforge.client.extensions.common.IClientItemExtensions > consumer) {
        consumer.accept(new IClientItemExtensions() {
            public HumanoidModel getHumanoidArmorModel(LivingEntity living, ItemStack stack, EquipmentSlot slot, HumanoidModel defaultModel) {
                HumanoidModel armorModel = new HumanoidModel(new ModelPart(Collections.emptyList(),
                        Map.of("head",
                                new UnderArmorModel<>(Minecraft.getInstance().getEntityModels().bakeLayer(UnderArmorModel.LAYER_LOCATION)).Body,
                                "hat", new ModelPart(Collections.emptyList(), Collections.emptyMap()), "body",
                                new ModelPart(Collections.emptyList(), Collections.emptyMap()), "right_arm",
                                new ModelPart(Collections.emptyList(), Collections.emptyMap()), "left_arm",
                                new ModelPart(Collections.emptyList(), Collections.emptyMap()), "right_leg",
                                new ModelPart(Collections.emptyList(), Collections.emptyMap()), "left_leg",
                                new ModelPart(Collections.emptyList(), Collections.emptyMap()))));
                armorModel.crouching = living.isShiftKeyDown();
                armorModel.riding = defaultModel.riding;
                armorModel.young = living.isBaby();
                return armorModel;
            }
        });
    }

    public String getArmorTexture(ItemStack stack, Entity entity, EquipmentSlot slot, String type) {
        return "nukaisl:textures/models/vault_suit_full.png";
    }

}

P.S. : Still learning both Java and forge and completely understand if this is just a me being stupid thing

Wow i kinda botched this post my bad haven't really made many of these!

I mean, this is not how you add a model. You register the layer definition to get the baked layer via EntityRenderersEvent$RegisterLayerDefinitions#registerLayerDefinition, then, construct the model only once using the EntityModelSet. You can construct the model during EntityRenderersEvent$AddLayers which contains the associated model set. You can roughly follow giga's gist on this.

57 minutes ago, ChampionAsh5357 said:

I mean, this is not how you add a model. You register the layer definition to get the baked layer via EntityRenderersEvent$RegisterLayerDefinitions#registerLayerDefinition, then, construct the model only once using the EntityModelSet. You can construct the model during EntityRenderersEvent$AddLayers which contains the associated model set. You can roughly follow giga's gist on this.

Thank you!