You must have 5 posts to be able to do that.
It prevents from people just arriving, and plugging their site or services in there.
Welcome to the forums by the way.
Yeah well I think they were reconsidering some things about that rule like letting you reply in threads just not post new topics. But I geuss that hasn't happened yet.
But the good news is, if you reply to this post, you will have 5 posts.