You need to create a blank database with preferably a user that is not root. The user needs to be able to create tables as well as all the other usual stuff.
You then look in the config.php file for something that looks like the following:
$cfg->dbtype = 'postgres8';
$cfg->dbhost = 'localhost';
$cfg->dbport = '';
$cfg->dbname = 'maharadev';
$cfg->dbuser = 'mahara';
$cfg->dbpass = 'putyourpasswordhere';
And change that to have the dbtype be "mysql5" and replace the credentials to be those for your new blank database.
The Mahara install script will connect to the database and helpfully build all the tables for you. You don't need to import them :)
https://wiki.mahara.org/index.php/System_Administrator%27s_Guide/Installing_Mahara has some instructions
Hope this helps,
Melissa