But with this "simple" config, I don't know what I should use to connect and how to add new addresses. My first guess is I create new addresses by creating new server users and passwords. Is that right?
I don't know the exact configuration, but if you're using a MySQL database with this setup, then the username probably is the email address. Otherwise, you probably have to create system users for your email accounts. This link might help: http://www.howtoforge.com/forums/showthread.php?t=2