If you are using typical web hosting, you can probably leave the first line as it is.
The remaining lines are for the database you must set up for Q2A to work - the username, password and database name.
If your hosting provider gives you a way to create MySQL databases, you should create one. Perhaps call it "myq2a". Then when it asks for a username and password, choose one: maybe "q2a" for the username, and something secret for the password.
Then you put these entries in your qa-config.php, and that is pretty much all you will need to do. If you visit the homepage of the site where you have installed Q2A, the installation process will do the rest.