Why am I getting an error?

[Eternalove_fan32 (FrostDracony)]

Its because you are not using str but self instead. So just add before the str parameter another parameter and name it self. Then it should work:

Set = function(self, str)
	label.Text = str
	return label
end

If you want to understand self, check out this post!

What is self and how can I use it?

You can write your topic however you want, but you need to answer these questions: What do you want to achieve? Keep it simple and clear! I would like to make a character controller of @EgoMoose se What is the issue? Include screenshots / videos if possible! I don’t know what self is. What solutions have you tried so far? Did you look for solutions on the Developer Hub? I don’t find a post that read about self. I don’t want you to write a whole code, but a simple example would be …