When you have set up your SMF forum, or wish to join another SMF forum, you should register a username. This will enable you to maintain a consistent identity while posting and keep track of what you've read, no matter where you're working from or what computer you're using. You'll be able to fill out a personal profile and use the built-in personal message system. You'll be able to subscribe to email notifications, monitor your forum activity and more.
How to Register
Assuming you've arrived at the forum as a guest and wish to register, you should be looking at one of these two things:
The Registration Screen