@nmd (View Post)
If you downloaded it, connect your iDevice to the computer and then:

Open iTunes
Select the device
Click "Update"
Since it's already downloaded, there shouldbe an option to install. If so, click it.

**If there is no "Install" option, the best option is to just download it it again. Click "Download & Install" and you should be set.**
**Be sure to sync your iDevice/allow iTunes to create a backup of it**

@BloodLust (View Post)
Yes, installing the new OS will completely wipe the device of all content. Be sure, as a move mentioned, to sync/backup the device before updating.

back up your device to your computer on itunes. when the new software is installed then it should automatically sync itself and you will get all of your apps and music etc back. thats what i did for my ipad 2.