From Online Manual
When a user sets up an SMF forum, or wishes to join another SMF forum, they should Register an account. This will enable them to maintain a consistent identity while posting and keep track of what they have read, no matter where they are working from or what computer they are using. They will be able to fill out a personal Profile and use the built-in Personal Message system. They will also be able to subscribe to e-mail notifications, monitor their forum activity and more.
When a person arrives at a forum as a guest, and they wish to register, they should be able to register by finding one of the following on the forum:
* Any page of the forum; they should select the Register link from the main menu. * A login screen headed by a warning about access being restricted to registered members;
they should either use the registration link provided on the login screen warning or select the Register link from the main menu.
When they reach the registration page, they will need to fill out details such as a username, password, and e-mail address.