You cannot report a prior year W-2 on your current year tax return. You can only include your 2016 W-2 on your 2016 tax return.
If you have an unreported Form W-2 from a prior year, you would need to file(if you did not file for 2013 and 2015 tax year) that year's tax return to report it. Documents must be filed with the tax year to which they were issued.
TurboTax Online works only for current year (2016) taxes, and not for any other year. If you want to use TurboTax for any other year you will need to purchase the Desktop Version for each year that you need to file. You can do that at the link below:
http://shop.turbotax.intuit.com/personal-taxes/past-years-products.jsp
Tax return for prior years can only be printed and mailed, it cannot be e-filed.
Tip: If you prepare multiple years of prior returns, mail each one to the IRS in a separate envelope to be sure that each one is recognized as a separate tax return.
