You cannot use TurboTax Online to file for 2017. TurboTax Online is only for the current tax year, which is now 2018. To file for 2017 you have to use the CD or download TurboTax software for 2017. 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 2017 in stock.
Tax returns for past years cannot be e-filed. You will have to print your 2017 tax return, sign it, and file it by mail.