Download iOS updates by using the Setting app on your mobile device or using iTunes on your computer. Create a backup of your device before updating its operating system.
To update the operating system on your device, open the Settings application, choose General, and tap Software Update. If an update is available, the device displays its contents. Tap Download and Install below the description, and enter your password if the device asks for it. Alternatively, tap the update notification when the device displays it.
To update via your computer, plug in the device, and open iTunes. Select your device from the list on the left, click Summary, then click Check for Update. If an update is available, click Download, then click Update.