When updating to ios 6
There have been instances with past i OS updates where users have reported the new i OS didn't install correctly, bricking their phone and forcing them to restore their phone before trying again.
So, if your i OS device has talked to i Tunes recently, go ahead and go to Settings You should see i OS 6 listed, with a Download and Install button below it.
To perform the update you must get a hold of the i OS 7 ipsw here.
Press and hold the Option key (Shift for Windows) and click Update in i Tunes if your device is not in Apple developer programme. Select the i OS 7 ipsw from the popup window to install. Only i Phone devices registered by developers are supposed to be able to install beta firmware.
Tap the button, agree to Apple's terms and conditions, and either heed or ignore Apple's advice to connect your device to a power source during the download to save battery.
After i OS 6 installs, your device will restart, which was a rather lengthy process in my experience (20 minutes or so, after the roughly 45 minutes it took to download and install).
In the event something goes wrong with your update, you'll always want to make sure you have a current backup.
You have two basic options for updating your device to i OS 6, either wirelessly over-the-air (which will take a while) or hook it up through i Tunes. If you want to update to i OS 6 OTA then go to Settings Software Update and pick i OS 6.
Tap through the setup screens and wait until the device restarts (it would be wise to plug it in, especially if the battery is low).
So if the update isn't showing up for you directly on your device and you just can't wait any longer to update, follow along to update the old fashioned way using i Tunes.
You'll need to make sure your device is capable of running i OS 6.