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.
Next you'll need to make sure you have the latest version of i Tunes which will be version 10.7.
You can either visit i to snag the latest update or if you're on a Mac, just run a software update and it should come through.
After downloading to i OS 8, you might encounter some problems, like puzzeleed on how to space up your device to get the i OS 8 installing package; the device gets frozen or stopped during i OS 8 installing; or the device stuck on Apple logo after i OS 8 updating etc, please refer to other posts to get help.
-- and you'll want to make sure you update in order to take advantage of all the new features i OS 6 has to offer.
2) Click the "Download and Install" button to begin download the i OS 8 installation package.
3) After the i OS 8 installation package is downloaded successfully, click "Install Now".
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.
But any time it does release an i Pod software update, you should install it.