> Install trouble
Short of storage? An over-the-air update may fail because the process needs more space to store the update. One solution is to use the latest version of iTunes on your Mac: open it, connect your device using its cable, click the device icon near the top left of iTunes and click Check for Update.
Once you’re on iOS 11, you can avoid this situation in future. Go to Settings > General > [Device] Storage. Accept the recommendation to offload apps if you are okay with iOS deleting apps when it needs space. To get one back, tap its Home screen icon. Or, you can manually offload an app: tap its name, then Offload App.
The ability to offload apps (but retain their data) is new in iOS 11. It can be automatic or manual.