Do you want to update to iOS 8 but haven’t got enough space on your device? There’s a way to get round the problem which doesn’t require you to delete half your apps: use your computer.
To do this, plug your iPhone into the computer using the USB-Lightning cable. This is the one that you use to charge your device as well. If you haven’t used the computer before then the iPhone will ask if you wish to allow the computer to access data.
Select Trust to allow the computer to communicate with your device.
Make sure you select Trust
Now open iTunes on the computer. It should prompt you that an update is available, but if not, click your device and select the Update option.
Update your device through iTunes
After you click this the update process will begin — this can take some time so be patient. Make sure to leave your device plugged in and the setup process will eventually complete, then follow the steps on your device to finish the upgrade. Now you can use iOS 8.