I installed Mybb and then went to login as admin with the new password sent to me. It let's me log in but then when I do anything at all it takes me right back to the login page every time so how can I stay logged in as admin?
Your cookies are set incorrectly. Need to make the match your website/installation.
+1 for Lith, this is usually a cookie problem, is your forum in a sub dir? You may have set the wrong setting for cookie path when installing your forum.. but don't worry.. this is easily fixable from FTP via the (i think) settings.php file in the INC folder OR the config.php file... I think it's the config.php file but I forgot.. someone else can verify this.
you will find all the information to correct your cookie problem in the sticky thread
HERE.