Well as already stated checking the manual would be my first step - your HP printer is in the list of those compatible w/ Apple's wireless printing technology called AirPrint - check HERE for further information.
Your iPad needs to be on the same 'wireless' network and the apps that you are using on the device need to offer an AirPrint option - the only other consideration might be the need for a firmware update to your printer - if you cannot get the printer & iPad working together check to see if you have the latest HP firmware on the printer (i.e. go to their website) - good luck and post back as needed!