You will need to file a return for 2015 to file for any income from 2015 (and include your Form W-2 from 2015). Your W-2 from 2016 will be entered in your 2016 tax return. You can only use
Turbotax Online to file for the current
year (2016) taxes, and not for any other year.
If you would like to
use TurboTax for any other year you will need to purchase the Desktop Version
for the specific year for which you need to file a return. You can purchase the
Desktop version at this link:
http://shop.turbotax.intuit.com/personal-taxes/past-years-products.jsp