Mainly, you just move all the files up to the home directory.
Apart from that, you should also change the URL within the admin panel.
The other problem you may have is with smilies embedded within posts via the WYSIWYG editor, which have absolute URLs. You can fix this by having a redirect on your server which re-routes requests to the q2a directory up a level.
This last issue will also ensure external links to your site still work.