Hello, I'm Nathan and I will be assisting you today. Please remember to rate/accept my answer when we have finished. Thank you.
Are you trying to print to the printer via wifi, from the ipad?
A few things to check: make sure your printer has the latest firmware installed.
Make sure ipad and printer are on the same wifi network. You may need to reboot your router (unplug power for 60 seconds)
If that doesn't help, try using a wired ethernet connection from printer to router if possible, and assigning a static IP address to the printer.
I'm sorry I don't understand what you mean by "download to your ipad"
You don't install the printer on the ipad, when you attempt to print from an app on the ipad with print functionality, it will scan the network for printers and if your deskjet is available, it will find it and print to it.
There is no downloading involved.