Go to: http://www.gopbloggers.com/
On the menu at the top of the page, click on "Grassroots"
then on the new page look for the 2nd menu from the top, click on: "Join The GOP Blogroll"
That's where you can sign up.
You know .. it's probably a silly to ask .. but don't you think clicking twice to Register is odd? Why not just have a buttom "Join the GOP Blogroll" at the top of the first page?