iOS update steps
Back up device.
Over 50% charge is required to install so if devise has less plug in.
1. Settings > General > Software update. If update available:
2. Tap Download and Install. Download to your devise in about 20 minutes.
3. Once downloaded you’ll be asked if you want to install Now. Installation could take up to an hour. (Or chose later and select options given.)
4. If asked to enter your passcode (code used to access you device) do it.
5. Message on your screen will advise when installation is complete.
Detail, maybe to detailed, instructions are HERE