But there's a safer, much better way to install iOS updates without the risk of deleting files: Wait till you're back at your computer and use iTunes:
- With iTunes running, plug your iOS device into your computer's USB port.
- Select your device from the Devices list. (Look for the Devices button near the top of the screen if the device pane doesn't appear automatically.) Go to the General pane for that device.
- Click Back Up Now to back up your iOS device's contents to iTunes. (While you're at it, check Encrypt Device; that way, your backup is safe should your computer be stolen -- and your passwords are backed up.)
- When the backup is complete, click Check for Updates. if there's an update, tell iTunes to install it. You won't need to worry about having sufficient working space on your iOS device because iTunes uses your computer for that instead.