Add printer on El Capitan
HP has its drivers readily available on its website. Just google the name of the printer.

That led me to this link. Which seems to have the driver you need.

Apple Software Update does not always have the driver you need. It has gotten so that any time I install an HP printer I just google the name for the latest driver as the CD that comes with most printers is Windows only or out of date. Also they often install a bunch of crap advertising HP supplies.