Took me a bit to figure this out too, but when you open the tax file from a prior tax year - it'll be hard to find the "Amend" option. TurboTax CD / Desktop versions consider Amendments as "New Returns", so the way to see that option is to first go to the top left hand menu / horizontal navigation bar and Select File > New Tax Return > then on that start page, if you look on the screen the "Amend" return option will appear as one of the options.
Hope this helps!
