Editing Already made signup page

I want to simplfy my registration page it has first last phone number date of birth etc etc...I want all of that deleted and I want it to just say enter email then enter the code displayed which is already on there then the next page is create user name and password which is already there as well so basically delete add the email make sure you can create the username and password and make sure it registers and allows you to login. I cant see this taking someone more then 30 minutes