To post a frag you need to register here: http://www.fragoutpost.com/registerUser.php
After you register and login just click the link that says "Post new frag".
vBulletin is an independent forum software which requires you to register seperately from the FragOutpost.com website. One day I might get around to integrating the two registration systems.
You should register for FragOutpost.com to post frags for sale or trade,
or to respond to a frag that has been posted on FragOutpost.com.
Let me know if you encounter any problems.