It's the tab that says "My iPhone Ringtones and Alert Sounds"
It's a very simple process... you download the ringtones you're interested in, (unfortunately, I haven't found a way for you to listen to these ringtones before you download them yet)... drag them from your downloads folder to iTunes, and iTunes recognizes this file type as iPhone Ringtones. You will then have a category on your left-side menu in iTunes that says Ringtones. You can listen to them there, delete the one's you don't like... and when you sync your iPhone, they should automatically sync with your phone!
Hope you enjoy! Feel free to leave comments for me if there are specific songs you're interested in...
