Just download and install i OS 8 on your device with the detailed i Mobie Guide.
Check How to Update to i OS 8 Over the Air or Via i Tunes Once the i OS 8 is installed on your i Phone, i Pad, i Pod touch successfully, most of you think the whole process is finished.
Find All Common i OS 8 Upgrade Problems and Solutions Have no plan to upgrade your device to the i Phone 6/6 Plus?
Beyond fixing flaws, the new i OS also has some neat features you’ll want to get your paws on.If you need more space for a wireless update, you can update using i Tunes or delete content manually from your device.Whether you use i Tunes or update wirelessly, you'll have the same amount of free space on your device after you update.Update your device wirelessly If a message says that an update is available, tap Install Now. Plug your device into power and connect to the Internet with Wi-Fi. If you see an error message while trying to update your device wirelessly, learn what to do. Or if you need more space for an update, you can delete content from your device manually.