How to send packets to client side ?

[Armanse]

Hello, recently i've been struggling with sending packets from the server to the client side. I understood the concept but i still don't know how to do it.

1) how do can i send a msg to the client side i did that :

public class ModPacketHandler {
	private static final String PROTOCOL_VERSION = "1";
	public static final SimpleChannel INSTANCE = NetworkRegistry.newSimpleChannel(
	    new ResourceLocation("mod", "main"),
	    () -> PROTOCOL_VERSION,
	    PROTOCOL_VERSION::equals,
	    PROTOCOL_VERSION::equals
	);
	
	public static void handle(String msg, Supplier<NetworkEvent.Context> ctx) {
	    ctx.get().enqueueWork(() -> {
	        // Work that needs to be threadsafe (most work)
	        ServerPlayerEntity sender = ctx.get().getSender(); // the client that sent this packet
	        // do stuff
	    });
	    ctx.get().setPacketHandled(true);
	}
}

But i don't know how to use it. And i don't even know if it is necessary.

2) I don't know what i have to put in the "msg" variable because what i want to do is send the position of a particules that has been determinated randomly by the server side so that they can be synchronized.

Any help or documentation will be appriciated. Thank you for helping

[Armanse]

MinesteriousPacketHandler.INSTANCE.sendTo("something i don't know what to put here but its a string", NetworkManger "here too..." , NetworkDirection.PLAY_TO_CLIENT); // On the last one i don't know what to put between PLAY_TO_CLIENT or LOGIN_TO_CLIENT	

that's what i tried to do for now ...