You can do a restore via your Mac. Even if you cannot see your screen, this guide can be used. Your Mac will notify you when your phone is connected and ready to Restore.
1) Turn off your iPhone completely
2) Connect your Lightning Cable to your PC / Mac
3) Connect the cable to your iPhone - the moment the cable is in your iPhone, press and hold the Home Button until the device enters Recovery Mode. Recovery Mode is a black screen, with a computer and a cable icon.
On your computer. Now you can select Restore.
Restore deletes EVERYTHING and restores your device to factory settings.