Very first, write question title more specific with the issue. Your question can be ignored if it doesn't interest to the person here.
For WP you do not need to set full path but relative from Q2A directory to WP directory where wp-load.php lies and that's on the root. So if www.my site.com is your WP site on server ROOT and Q2A is www.mysite.com/qa means ROOT/qa.
You need to define WP path as ../
Of course you have to setup qa-config.php but the database credentials will be the same as WP db, since it will be installed in the same database.
BTW this answer has been given many many time from many people here. Just couple of days before I explain this on one question here.