OnSong gives you many ways to export songs from one device and use on another. Using the OnSong Archive file format will allow you to transfer songs and retain all the styles and settings of the original version. To get started, open the Songs Menu by tapping on "Songs" in the Menubar. If you haven't already, you'll want to select a collection or book to export. To export all songs, you'll want to select the All Songs collection from the Books Menu.
Next, tap on the + button on the bottom to open the Add Songs Menu. While this is counterintuitive, you'll find an Export section at the bottom of the menu. Choose Dropbox or iTunes File Sharing to open the Export Menu with the songs in the selected collection preselected for export. You can change items in that selection by tapping on the "papers" icon in the lower left to open the Song Picker. Next, tap on the wrench icon to open the Output Options Menu and turn on the "As a single file" option. This will allow all the songs to be transferred as one file, instead of separate files. Finally, choose tap on the OnSong Archive file format to select it and then tap the Export button to create the file.
To add these songs to another device, simply import the OnSong Archive file or files.