Here's how you can upgrade iOS without having to sync it with iTunes. Instead, you can update iOS via the over-the-air software update. It's much easier and faster than messing around with iTunes. 1. Launch the Settings app and tap on General. 2. Tap on Software Update. 3. Tap on Download and Install if there's an iOS software update available.
For more, see the original article at the link below.
How to Use Over-the-Air (OTA) Software Update on iOS | OS X Daily