update-to-ios-83

The iPhone 4S and later, iPad 2 and later, and iPod Touch (fifth generation) can run iOS 8.3. Unsure about the device model? Plug it into your computer, open iTunes, and the model as well as the currently installed version of iOS are listed under the Summary tab. You'll also need to know the device's passcode in order to update. iTunes will prompt you to unlock the phone or tablet once it's connected.
Alternatively, you can access the "Back Up Now" button under Summary in iTunes. Double-check your work by clicking the iTunes top menu > Preferences > Devices tab. You should see the name of the device and the time of backup.
On the device, update by opening the Settings app, tapping on General, and selecting Software Update. You can also connect the device to a computer and find the software update button next to the backup section.