There are two types of audio files that Bookmobile and Book Mower can play: DRM-protected (Digital Rights Management) and non-DRM. DRM-protected audiobooks are typically from the Apple iTunes Store or Audible.com, andmustbe stored in your iTunes Library on your iOS device to play. The app does not copy the files once they are on your device. They remain in your on-device iTunes library, and you manage them using iTunes exclusively. The app plays the audio directly from your iTunes library.
There are only two ways to add audio files to your iTunes Library: direct purchase from the iTunes Store on your device, or syncing iTunes with the computer that hosts your iTunes library. If you sync with your computer, you must specify in iTunes what audiobooks you want to transfer.
The iTunes app on your computer also supports storing and syncing many other types of non-DRM files. These can be mp3 files coming from CDs, downloads from the Internet, or podcasts subscribed to in iTunes. These non-DRM files are transferred to your iOS device in the same way the DRM files are.
Once the audio files are synced onto your device, you add them to the app by first tapping on the "+" button on the bottom of the screen, then tapping on one of the options: Add All Audiobooks, Add Audiobooks, Add Podcast* and Add Music Files.