Restoring the iPhone using iTunes will result in the loss of all data stored on the device including 3rd party applications.
This type of reset should only be used as a last resort after all other troubleshooting steps have been exhausted. It is highly recommended that you complete a backup of the device information before proceeding with the steps in this tutorial.
The computer will need to have the latest version of iTunes installed. iTunes can be downloaded from the Apple website: http://www.apple.com/iTunes
Connect the iPhone to the computer using the supplied USB cable.
Open the iTunes application on the computer, then click the iPhone icon.
Click Restore iPhone.
Note: If prompted to automatically check for iTunes and iPhone updates, click Check.
If prompted to back up the settings, click the preferred option.
Read the iTunes alert message and click Restore.
Note: If prompted to turn off Find My iPhone, read the prompt to disable it, then click OK.
Click the Next button in the iPhone Software Update window.
Read the software license agreement, then click Agree.
iTunes will begin restoring the iPhone to its default settings. Do not disconnect the iPhone from the computer.
When the Welcome to Your New iPhone screen is displayed, the restore is complete.
Note: To set the device up, select the desired option and follow the prompts.