You cannot use TurboTax Online to file for 2016. TurboTax Online is only for the current tax year, which is now 2017. To file for 2016 you have to use the CD or download TurboTax software for 2016. 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 for 2016 in stock.
TurboTax does not allow returns for past years to be e-filed. You will have to print your 2016 tax return and file it by mail.