Creating the content for the iPad app is done through the Content section of the app builder, the same way you do for the smartphone app.
The same content modules that you used for the smartphone app, can be used to populate your iPad application.
Full list of available iPad content can be found here.
If you navigate to the Design Tablet tab, you'll see your existing content sources to the left of the iPad preview screen:
Click on one of your feeds and drag it to anywhere you'd like in your iPad app layout: