hp photosmart a646

Hello,

I have an HP photosmart a646 printer which I had been able to use with iphoto. Now that photos took over for iphoto and i can't open iphoto anymore I can not use the printer. It's connected by usb to the imac and it's not coming up under printers and when I go to run the installer it says it cannot be installed on my computer bc it has to be updated to 10.4 or later but I'm running 10.10. I downloaded the HP printer drivers for the updates but that's not helping any either. Any advice? Thanks.