You cannot use TurboTax Online to file for a past year. TurboTax
Online is only for the current tax year, which is now 2018. To file for
an earlier year you have to use the CD or download TurboTax software for
the year that you need to file. You can purchase a download at the
following link.
http://turbotax.intuit.com/personal-taxes/past-years-products.jsp
You might get a better price from a reputable online seller that still has TurboTax in stock for the year that you need.
Tax returns for past years cannot be e-filed. You will have to print your past-year tax return, sign it, and file it by mail.
TurboTax for years earlier than 2015 is no longer supported. If you purchase an earlier year from a third party it almost certainly will not work correctly.