1. Update to the latest version of iTunes.
  2. Open iTunes and connect your device to your computer.*
  3. If a message asks for your device passcode or to Trust This Computer, follow the onscreen steps. If you forgot your passcode, get help.
  4. Select your iPhone, iPad, or iPod when it appears in iTunes. If your device doesn't appear in iTunes, learn what to do.
  5. If you want to save Health and Activity data from your iOS device or Apple Watch, you need to encrypt your backup: Select the box called Encrypt [device] backup and create a memorable password. If you don't need to save your Health and Activity data, you can make a backup that isn't encrypted. Just click Back Up Now.

    Write down your password and store it somewhere safe, because there's no way to recover your iTunes backups without this password.
    iTunes summary pane
  6. When the process ends, you can see if the backup finished successfully on the Summary screen in iTunes. Just look under Latest Backup to find the date and time.
    iTunes summary pane