I have Lion with AirPort Utility v.6.3.1 and there doesn't appear to be any Manual Setup located anywhere within the utility.
Open AirPort Utility 6.3.x
Click on the picture of your Base Station
Click Edit in the smaller window that appears
(Edit is now the substitute for the Manual Setup button in earlier versions of AirPort Utility)
When you do this, you will see that the pull down under the Base Station menu is no longer greyed out. There are also tabs for various settings for the Base Station, Internet, Wireless, Network, Disk, etc. Take a peek at each tab to get an idea of the next layer of settings.
The Base Station menu item at the top of the screen displays Add WPS Printer, but you can install any wireless device using this method....at least any that I have tried.