To install your printer, run VASMCC ("Start" menu, System, VASMCC, or click on the icon in the Panel at the bottom of the screen). Click on Services, CUPS Printing. This will start a browser. Click on Add Printer. Work your way through the screens. Under Make/Manufacturer, pick HP and scroll to Deskjet 1120C. Finish the setup.
Once the printer is installed, click on Set Printer Options under the Printers tab while still in CUPS in your browser. Then Print Test Page. If all is well, you're ready to use the printer. If you run into a problem, post about it here.