It doesn’t make sense how to get a face ID so I might be trying again later on

The question is that how am I supposed to do the Face ID so it’s gonna be a hard . if you can’t be really hard because my brother knows how to do this, but I’m not gonna ask him because he’s asleep. I don’t wanna make him awake because he will get mad at me and I just wanted to say that is it might be pretty hard to do this face ID so you’re gonna have to help me with that stuff because I don’t know how to do that because I’m only eight years old and I don’t know how to do only on my phones and stuff like that.