Well for a start you want to make sure you have the drivers installed. HP is OK about having the right drivers, but just in case you should get
Gutenprint. It's a set of open source printer drivers and whenever a company doesn't have it supported, these guys do. And even when the company does, this driver is usually works better. I have it installed on mine, never fails. Also, yours is listed.
Second, you must connect to it over the network.
(1) Connect to your network the way you normally would, be it via wi-fi or ethernet, then open up Printer Setup Utility (/Applications/Utilities/Printer Setup Utility.app).
(2) Once in the program click the icon in the menu with a "+" that is labeled Add. This will bring up the printer adding dialogue. It will do a bit of a search, if your printer doesn't come up there, click "More Printers" in the bottom right of the window.
(3) This brings in a pane and you need to choose "Windows Printing" in the top drop-down list and "Network Neighborhood" in the lower drop-down list. In the text area you should see a series of names, or only one, it depends on how many networks you're connected to. If it's only one, you know which to select. If it's more than one, select the one the computer with the printer is on. Double-click the network to view the list of connected computers.
(4) From the list of connected computers select the one that you know the printer to be connected to. You'll probably be asked a name and password, just type it in.
(5) This time the list will change again to a list of the printer or printers connected to the machine. Click the one you want to connect, but don't click add just yet.
(6) Once the printer is selected, choose the brand of printer from the drop-down list labelled "Printer Model" then select the specific model of printer from the generated list. Now, you can click Add.
Now back in Print Setup Utility you'll see the new printer listed with all the others you have added, if you have any at all. Now just go and print as you see fit.
