It's different for all printers though, gina (though you may be correct, it's not certain)
Click on your start button, select control panel > hardware and sound > printers.
When you can see the printer then right click on it and select properties, once the driver properties come up you should (hopefully) have a maintenance tab, click on that and look for a button labelled something like print head alignment and from that point you should be able to follow the instructions on screen.
(if it doesn't work then next thing to know is are they genuine HP cartridges or not?)