That’s right, deleting photos and apps, is not necessary. As it turns out, upgrading to iOS 8 just takes connecting the iPhone to iTunes.
Lets make it simple.
Open up iTunes, connect your iPhone.
Download and install the new iOS 8.
As always with any computer device, it’s a good idea to back up your phone before making any changes.
And that’s all.
Not connecting to iTunes? If the iPhone has 5.6 GB of space just be sure to connect the power so that it completes the upgrade properly.