BuddyPress.org

As Peter said, with the bp-sn-framework, is simpler, you need to add in the style.css at the top in the comment-header

/*

[….]

Template: bp-sn-framework

*/

deactive your current theme and reactive it again. (Remember it works only with 1.1-svn version).

You have to put css you want in your style.css and they will be applied on the default registration page.

Or you can copy from the bp-sn-framework the register.php to your theme dir, and edit html if needed

Nicola