I assume that you have a HP DeskJet 990. In order to access this printer wirelessly, it can only be networked by connecting it to a print server. The print server must, in turn, be connected to a wireless router. The server may be a computer or it may be a dedicated server.
At any rate, your printer does not have manufacturer support past MacOS X 10.5.x. The
HP DeskJet 990 does, however, have
CUPS support by the Linux Foundation's OpenPrinting Project. Better yet, install
Gutenprint which includes the HP DJ 990c driver as well as documentation for Apple's
CUPS.