the dl the drivers. install them. log out and back in (for good measure) and then go to /Applications/Utilities/ and run print center.
if it isnt there call hp and ask for help. if it is make it the default.
gimp-print is a management system for printer drivers (like print center on CUPS) used in most nix's including but not exclusively linux. dont worry, it is a bit advanced for most people as it is fairly much a terminal affair.
good luck