To restore copies of your content and settings to iPod touch, you must first create a backup of your iPod touch. See Back up with iCloud Backup and Back up iPod touch with iTunes.
If you’re asked to enter your passcode or Apple ID password and you’ve forgotten either, see Forgot your Apple ID, iPod touch passcode, or iCloud Security Code?
Erase then restore iPod touch from a backup. Go to Settings > General > Reset, then tap Erase All Content and Settings. After iPod touch restarts, follow the setup assistant to restore iPod touch from an iCloud or iTunes backup.
Restore iPod touch from an iTunes backup. Connect your device to the computer you normally sync with, then in iTunes choose File > Devices > Restore from Backup.
Restore iPod touch to factory settings using iTunes. Connect your device to a computer, open iTunes on the computer, click the iPod touch button near the top of the iTunes window, then click Restore iPod touch in the Summary pane. All of the content and settings on iPod touch are deleted, and the latest iOS software is installed.
Important: Restoring iPod touch to factory settings using iTunes deletes all your content and settings, but doesn’t erase it. Deleted information can’t be accessed through the iPod touch interface, but it remains on your device. For information about erasing all content and settings, see Erase iPod touch.
For more information, see the Apple Support articles Restore your iPhone, iPad, or iPod touch from a backup and If you can’t update or restore your device. For more information about iTunes, refer to the Help in the app.