To update your iDevice with iTunes, you need your iDevice, a USB cord, and a computer with iTunes installed. Open iTunes and plug in your iDevice using the USB cord. iTunes will recognize your device and bring you to the summary page, where you click "Check for Updates" or "Update". You may need to agree to Apple's terms and enter your computer password before clicking "Okay" to start the update process. While updating, do not use iTunes or the iDevice until iTunes indicates the update is complete.