You must confirm your membership via an e-mail once completing the registration process. An e-mail is sent after completing the process here, but that's only the first step and the second step must be completed or you will not be able to post anything.

Starting immediately... I'm going to start deleting unconfirmed registrations on a "once a month" basis.

So, check your e-mail and also check your email providers spam folder as well. The forum software works on this end and emails are going out. If you aren't receiving the conformation email then you need to adjust your inbox settings from your ISP to allow emails to go through and be allowed.