How can I make an Idle Animation?

So basically I have been watching a few tutorials on how to do this. And as of now, none of them work. I put the right Id, and e.t.c. Here is the script, it is a very popular one: https://pastebin.com/ynigQMMd. If you are going to answer this, please tell me if it should be looped, and what kind of Animation it should be, what I mean by what kind of animation is the Core, Movement, Action, and Idle.

Thanks, and I'll link all the things you need to help me.