Add a patient to the queue and tap on the "Notes" tab

Tap on the "New Note" button 

Tap on the RX template

Press the "+" button

You can search for the medicine that you need. You can also add your own.

Tap on the "Add to Favorites" checkbox to save the medicine. You'll be able to use it next time when you tap on the "Favorites" tab.

Tap on the "Create" button to add to your prescription.

If you want to add more medicine, tap on the "+" button again to add more.

Once you are done, simply tap on the print button on the upper right side

Pick the paper size

You will see a preview pop-up of how the prescription will look like when it's printed out.

If your AirPrint printer is powered on, then you'll be able to see it there. Tap on the "Print" button to print the prescription.