Guest Ben, first you must sign up for the Archives, which you will find here: http://www.adult-fanfiction.org/html-index.php
Once you have done that, you can follow the steps detailed here: http://www2.adult-fanfiction.org/forum/index.php/topic/25953-joining-the-forum/ to join the forum.
And in the future, please post questions such as this one in the appropriate forums, either the Software forum, or General Staff Questions.
And please note, this is an actively moderated forum, and archive, and you MUST be 18 years old or older to be a member of either one.