Connect to iTunes and back up. Open iTunes on your computer, then connect the device to your computer. Click the iPod touch button, then click Summary in the sidebar. To create a manual backup, click Back Up Now. To turn on automatic iTunes backups, click “This computer.” iTunes automatically backs up iPod touch when you connect it to your computer.
iTunes backups don’t include:
Content from the iTunes Store and App Store, or PDFs downloaded directly to iBooks
Content synced from iTunes, such as imported MP3s or CDs, videos, books, and photos (see Sync with iTunes)
Photos already stored in the cloud, such as in iCloud Shared Streams, My Photo Stream, and iCloud Photo Library
Activity, Health, and Keychain data
To back up this content, select “Encrypt local backup” in iTunes.
View or remove iTunes backups. Open iTunes on your computer, choose iTunes > Preferences, then click Devices. Encrypted backups have a lock icon in the list of backups.
Encrypt iPod touch backup. In the Summary pane, select “Encrypt iPod touch backup” if you want to encrypt the information stored on your computer when iTunes makes a backup. Encrypted backups are indicated by a lock icon 
, and a password is required to restore the backup. If you don’t select this option, other passwords (such as those for mail accounts) aren’t included in the backup, and you have to reenter them if you use the backup to restore iPod touch.
If you replace your iPod touch, you can use its backup to transfer your information to a new device. See Restore iPod touch.
For more information, see the Apple Support article About backups for iOS devices.