If you printer is connected to the network along with your iPad you can print photos straight from the photo app. Select a picture you want to print, click on the share icon, and scroll at the bottom till you see a printer icon. Next click select printer and you should see the printer in the list.
Depending on the type of printer you have it might have a native app for iOS from the manufacturer. Check the app store and the manufacturer's website to see if one is available.
You can also use a number of free and paid apps both that connect you to the printer directly or through a computer.