Restore all content to iPhone from a backup
You can restore content and settings from a backup.
Erase then restore iPhone from a backup
Important: You must first create a backup of your iPhone. See Back up iPhone using iCloud or iTunes.
Go to Settings > General > Reset.
Tap Erase All Content and Settings.
Follow the setup assistant when iPhone restarts.
The setup assistant gives you the option to restore iPhone from an iCloud or iTunes backup. (See Turn on and set up iPhone.)
Restore iPhone from an iTunes backup
Important: You must first create a backup of your iPhone in iTunes. See Back up iPhone using iCloud or iTunes.
Connect iPhone to the computer you normally back up to.
Open iTunes on the computer, then in iTunes choose File > Devices > Restore from Backup.
See the Apple Support articles Restore your iPhone, iPad, or iPod touch from a backup and If you can’t update or restore your iPhone, iPad, or iPod touch. For more information about iTunes, refer to the Help in the app.