If you're using Panther you might have some special issues keeping you from printing. Panther, Airport, and certain printers just don't get along.
Here's how it should work, in as step-by-step a fashion as I can put it. Install your printer driver/software--you'll probably have to restart. Plug the printer into the AirPort and turn it on. Open Printer Setup Utility, which will bring up the printer list. Click on ADD. Select "Rendezvous" from the drop-down list and you should see your printer listed in the box. Select the printer and click add. Your printer is now set up. Open something and print a test page.
Better this time?