User Registration Problem

http://www.antiaginginsights.com
I have a problem regarding user’s signing up. I don’t know how they are getting to that sign-up page. Visitors come to my website for a free eBook. I now have almost 8000 registered users but I cannot get to or see the user registration page where all these people are signing up? It is causing a big problem for me because I have to copy and paste them all over to Aweber and I cannot keep up! Any help would be greatly appreciated.