What do you type in at the field for 'MySQL Database [text field]

Any info on what to type in here?

The database name you created in your webhosting panel. Or manually via mysql.

luceos Just ran into another problem, seems like theres here:

Fatal error: Call to undefined function Composer\Autoload\includeFile() in /flarum/vendor/composer/ClassLoader.php on line 301

What PHP version are you on?

5.6.31