Printer not AirPrint compatible

Hi,

Any information about the exact printer make and model?

As ProustGiulio mentioned, there may be a special (iOS) app from the manufacturer (for network printers).

If the printer is a USB-only model, a third-party app like Printopia could make a Mac act as a print server, allowing printing from an iPhone connected to the same Wi-Fi network as the computer.

You don't, sorry, unless your printer's manufacturer has a specific app (related to your model) to download from AppStore. I would contact their support team and check.

Regards

Giulio