To enable automatic backups for OnSong, open the Utilities Menu by tapping on the gear icon in the Menubar and choosing Backup. This will open the Backup Screen where you can configure OnSong for automatic backup.
Select a location where you would like to export the backup file. The best practice is to export the backup file to a cloud service such as Dropbox or Google Drive. That way if you lose your device or it becomes damaged or stolen, your information is still safe off the device.
You'll want to name the backup file. By default, OnSong uses the creative name of "OnSong". If you're backing up multiple libraries or devices, you may want to name the backup file accordingly. You will also likely want to keep the "Append a timestamp to the filename" option turned off. If this is on, the filename will be unique and cause multiple duplicate backup files to be generated.
The last section of the screen lets you choose when OnSong backs up your library. If automatic backup is enabled, use the + and - buttons in the bottom field to adjust when this happens. By default, OnSong will backup and upload your backup file when you leave OnSong.
When you're all done, just close the screen, or tap on the Backup button to begin the backup immediately. You can learn more about the backup and restore process in the Backup Tutorial Video.