You can find a description with pictures in the User Manual of SongBook+ in the chapter "Backup and restore your data".
Here is a short summary:
- Stop SongBook completeley, it also mustn't run in background:
- Doubleclick the Home-Button on iPad, the list od running apps appears on bottom of the screen
- Long-click the icon of SongBook in that list on bottom until it gets a small red "minus" sign
- Click this "minus" sign to end SongBook completeley
- Click the Home-Button again to come back inti the normal view
- Open iTunes and go to "File Sharing" as you do to add documents.
- Copy your saved files from the computer back to the iPad using the button "Add..."