Add to the registration process

I wasn't quite sure what category to put this in, but anyway, I would like to add some things to my registration process

Firstly, above the "register" button, I would like to have a small disclaimer about the website, and explain that it is strictly 18+

Also, I was wondering if there is a way to have people fill out profile info upon registering, or add other things for them to fill out besides just the username, password and email.

I would like to add "age", and other things like that too, and perhaps blank fill ins (with questions above them)

Thank you for your help!!