You need to find the host name for the printer.

Go to the HP printer you want to use, and find the "Print Configuration Page" option. Usually this is under "Information". This step is not mandatory - sometimes you can guess what the host name is (see step 4).

Printout in hand, open System Preferences.

Open Print & Fax, and click the + button.

Protocol: Select "HP JetDirect - Socket"

Address: Enter the "Host Name" under the JetDirect section from your printout. If you don't have a printer configuration page, you can usually guess at the host name using the printer model and room number. Example: a LaserJet 3600 in room 225 would have a host name of HP3500-225. Since printers move around, this convention may not always hold.

Queue: Leave blank

Name: Enter Something descriptive Location: Room number, or office name

Print Using: The default should be fine.

Click Add

Enter as much information here as you can figure out from the printout. If you don't know what something means, you probably don't need it. You can always ask the help desk for help. After this step you should be good to go.