Can I install iOS 7 OTA (over the air)?
Yes, Apple will deliver iOS 7 over the air (OTA). A few conditions must be met for your iOS device to update OTA.
The device must be connected to Wi-Fi with over 50 percent battery remaining, or be plugged into a charger. There must also be enough empty space on your device to accommodate the new firmware.
Navigating to Settings -> General -> Software Update -> Install Now will get the process started.