If your iPhone crashes, you can reset it and restore the phone using the Apple iTunes application. iTunes lets you back up, restore and update the Apple iPhone software. If you do not have a backup of the phone's information, iTunes restores it to the latest backup, which resets the phone to its original settings.
Connect the iPhone to your computer using the iPhone USB cable. iTunes will automatically open after the phone is connected to your computer.
Click the "iPhone" icon in the left navigation panel. Click the "Summary" tab in the details panel. Click the "Restore" button to open the reset options.
Click "Don't Backup" to skip the option. Click "Restore" to start the reset process on the phone. After the restore process is complete, click "OK" to close the window.
Click the "Eject" button next to the iPhone icon in iTunes. You can now safely remove the iPhone from the computer.