Hi, welcome to iPF!
There are a few things you could take a look at, when trying to print:
Make sure the printer is turned on. Wait for a minute, sometimes the iPad doesn't find the printer immediately.
Printer and iPad have to be connected to the same Wi-Fi. AirPrint will not work in any other case.
Make sure you're within range of your printer, when you try to print for the first time.
The printer must have the latest software installed.
You can't print from every app. Safari, Pages, Photos, ... can print directly, as well as some apps from App Store.