Registering custom entity

Hello,

I need help with registering custom entity. A am using this code:

net.minecraftforge.fml.common.registry.EntityRegistry.registerModEntity(ResourceLocation registryName, Class<? extends Entity> entityClass, String entityName, int id, Object mod, int trackingRange, int updateFrequency, boolean sendsVelocityUpdates)

But I have no idea what the ResourceLocation registryName is. I watched a tutorial and there was nothing about it. I even looked to the source code of other 1.11 mod and there was no ResourceLocation registryName in registerModEntity at all. But for me, the game crashes without it.

Thanks for help