I just set this up on plus, so it can be done. Do you still have the email they sent you when you activated your MYSQL Database? If so, you need to enter that information as follows:
define('DB_NAME', 'DB Name')
define('DB_USER', 'Username')
define('DB_PASSWORD', 'Password')
define('DB_HOST', 'MySQL Host')
You will then have to set permissions as detailed in this post on the plus.net forum http://portal.plus.net/central/forums/viewtopic.php?t=30620 and that should do it.
