how to update ipod 4G version 4.3.3 with IOS 5.1.1

Update it from iTunes on a computer as described at the bottom of this article; there isn't a Software Update option in General on iOS versions prior to 5.0. It can only be updated directly to the newest iOS release supported by the device’s hardware, which is iOS 6.1.6 for a fourth generation iPod touch.

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