Registration form and Login button

I have two kinds of membership, Platinium and Golden. One more category as simple visitor who can get one free trial of my services. I made already the levels and private content of the pages inside my WP platform. But I don’t get it where can I customize fields of the registration page. Been clear, I need to know this issues:

1. How can I customize the registration fields?

2, Where can I edit or put my login button?

3. Where it goes the data that I obtain with the registration form?

I appreciate any kind of support with this….