There are two ways to update the iOS on your device either through wifi or using iTunes. The easiest way to update your device is wirelessly.
Update your device using wifi
1. Tap Settings > General > Software Update.
2. Tap Download and Install. Updates might download automatically while your device is connected to wifi.
3. Tap Install, or tap Later to install the update later. If you use a passcode, you'll need to enter it before installing the update.
Update your device using iTunes
Install the latest version of iTunes to your computer.
- Plug in your device to your computer.
- In iTunes, select your device.
- In the Summary pane, click Check for Update.
4. Click Download and Update.
The following content was provided by Apple Support.