What tax year are you amending?
To amend a tax return using TurboTax you must either be using the TurboTax desktop editions for the tax return that was completed and filed using the desktop editions. Or you are using the Amend software you downloaded from the TurboTax website for online tax returns.
If the W-2 appears to be entered twice then delete the second W-2 in the Wages and Income section. Follow the instructions for amending the tax return if you received a W-2C from your employer.