Printing With AirPrint
1. Install the printer. In order to print to an AirPrint printer, it must be connected to the same wireless network as your iPad. Each printer has a specific way to connect it to the network, but generally you’ll need to ensure that the network name and password are entered correctly.
2. Open the item you wish to print. On your iPad, open the item. You can only use AirPrint with programs that support it, such as Safari, Mail, Pages, and Photos.
3. Click the Action button. This button is located on the top bar of the program screen, and looks like a rectangle with an arrow coming out. This button will open a menu of actions you can perform. Select the Print button.
4. Select your printer. If you have more than one AirPrint printer on the network, choose the one that you wish to print from. Select the number of copies you want to print, then tap the Print button.
Here is a great HP Support page on printing wirelessly from an iPad or mobile device.