No, you cannot add a W2 from a prior year on your current return. You would have to file your 2011 return to claim the W2 income.
To do your 2011 return using TurboTax you need the
desktop tax software and the return must be mailed in you cannot efile a prior
year return. A prior year return cannot be done online, the Online version is
only to prepare the current year’s return. You can go to the following website
to purchase and download TurboTax’s 2011 desktop tax software.
http://turbotax.intuit.com/personal-taxes/past-years-products.jsp
Or, You can go to the IRS website to get Prior Year Federal Forms,
Instructions & Publications to manually do your returns (enter your form
number in the find box)
http://www.irs.gov/app/picklist/list/priorFormPublication.html
If you need to file a State return you can go to your
State's website for prior year forms to manually fill out & mail.
You can also check a website like Amazon.com for prior
year TurboTax software