I just checked, and you didn't buy the forum addon (during the signup process there is a page with 4 checkboxes, one of which is labeled "Forum System").
If you head to Admin, you'll see a button at the top labeled "Upgrade Service", above which reads "You don't have the full service. You are missing the following features:Loot Systems, Forums, Forum Uploads"
Click that "Upgrade" button, and fill out the form accordingly, and your Forums will be enabled.
