There are basically two ways to install i OS 8 on your i Phone/i Pad/i Pod touch- Over the Air (OTA) on your i OS device or via i Tunes.
Follow the Step-by-step instructions to install i OS 8 on your device now.
However, for a selectively backup and freely i Cloud management, Any Trans would be the best option for you.
It combines Data-Transfer, Device-Backup and i Cloud-Management all in one software.
Although i OS 8 is not the latest i OS version, you still need to upgrade to i OS 8 and i OS 9 firstly before upgrading to the latest i OS 10.
Before performing i OS update on i Phone i Pad, it is strongly recommended to do some pre work before you do any update.
Backing up your device before updating to i OS 8 is quite a vital step, and it can be easily accomplished via i Tunes or i Cloud.
You should make sure that the network or Wi-Fi connection is stable, and have your device fully charged before downloading the i OS 8 installation package.
1) On the homepage of your i Phone i Pad or i Pod touch, open Settings and click the "General" option, and then select "Software Update".
Then follow the Step-by-step instructions to install i OS 8 on your device now.The easiest way to get i OS 8 on your i Phone/i Pad/i Pod touch is to install i OS 8 directly from your device.