So you can get the Overdrive app with the iPad. You (after making sure the wifi is turned on) go into the appstore, and just do a regular search for "Overdrive".
Once it's downloaded, authorize it through the settings (using an Adobe ID, which you can use on up to 5 devices).
From there, you add a library, and can go and check out books.
Really, it's no different than using the Overdrive app on an Android. The big difference for me is the swiping motions and the back button.