If you forgot your password you can reset it by following these steps:
Go to the SMF script --> Click on 'login' --> Click on 'Forgot your password?' --> Type your 'Username/Email:' from the registration --> Click 'Send'
You will receive e-mail with link which will force new password to be typed.
If you've misspelled the email address when registering or do not remember it, there is another way to force new password change:
Log in cPanel and click on 'phpMyAdmin' from the Databases box.
On the top left box select the database of your SMF. Then click the edit button for the 'smf_members' table --> Find the administrator user and click the pencil button to edit it --> On the field 'passwd' where something like this will stand 'e6053eb8d35e02ae40beeeacef203c1a' change it with the one below. Then click the 'OK' button.
c435fc4b8ad32ee97ec39c636ee9b644ca2c7c57
Now your password is changed to sg123 and you can use it to log in. Then change your password to a new one.