These are the directions for installing previous in-app purchases into a new iPad installation...
I bought an upgrade on my iPhone. How do I get it on my iPad?
A: You can install your upgrades on up to five devices if you log into the devices with the same iTunes account. When the upgrade list opens, tap the Reinstall button......
Where is the Reinstall button? I've already downloaded the main app to my new iPad, but don't understand how/where to find this button.
Perform one of the actions that requires an upgrade, as described here:
http://www.arlomedia.com/apps/setlistmaker/support/upgrades.html
Then the upgrade window will open, and the reinstall button is in that window.