Utilities
Press the Menu 
from the Backup screen, and select Settings > Security and select the check box. And after enabling encryption, To restore synchronised organizer data, you must have an activation password.
NOTE:
You can also enable automatic delete old backups and only keep the most recent backup. Press the Menu 
from the Backup screen, and select Settings > Scheduled backup > Auto delete old backups to select the number of scheduled backups to keep.
