adding extra fields to the Membership registration page

Hi Guys. I know you've answered this many times, but I'm completely confused.
I need to add extra fields to my registration form to comply with legislation (political site). I see you recommend using Buddy Press but I can't figure out how to 1) find their registration form from the back end and 2) integrate it without using Buddy Press on the site. I should also add that, should I be compelled to use BP to accomplish the desired result, I certainly don't want it to be running in the site! I had a look at Protected Content, too, but to be perfectly honest, after Membership, I'm finding Protected is confusing in its setup. Perhaps I'm just over trying to figure out the best way to fix my membership-woes... Hope you can steer me in the right direction - you usually do!
Cheers.