Restore your iPhone, iPad or iPod touch in iTunes on PC
You can use iTunes to reinstall the software on your device and restore it to its default settings. You might need to do this if you’re having problems with the device (for example, if it freezes or stops responding frequently) or if you’re getting ready to sell it or give it away.
Important: Restoring software on iPhone, iPad or iPod touch deletes all your information and settings. However, iTunes backs up your device before restoring it, so you can use the backup to restore your device to how it was when you last used it. See Back up your iPhone, iPad or iPod touch.
Connect your device to your computer.
You can connect your device using a USB or USB-C cable or a Wi-Fi connection. To turn on Wi-Fi syncing, see Sync iTunes content on PC with devices on Wi-Fi.
In the iTunes app
on your PC, click the Device button near the top left of the iTunes window.
Click Summary.
Click Restore, then follow the onscreen instructions.
Restoring software on your iPhone, iPad or iPod touch erases all your information and settings. To find out more about erasing all content and settings, see the Apple Support article Restore your iPhone, iPad or iPod to factory settings.
If you turned on Find My iPhone, Activation Lock is on. You need to turn off Activation Lock before the new owner can activate iPhone for their own account. For information about turning off Activation Lock, see Remove a device from Find My iPhone on iCloud.com in the iCloud User Guide or the Apple Support article Activation Lock for iPhone and iPad.
Important: Before disconnecting your device from your computer, click the Eject button 
.