See this TurboTax support FAQ for completing a prior year tax return started with the online editions - https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turb...
You will also need the 2016 tax data file from the 2016 Timeline so that you can open the data file to continue the 2016 tax return after installing the 2016 software. In the desktop edition click File>Open Tax Return
To access your prior year tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show. Click on the Year and Click on Download .tax file
If you paid for one of the 2016 online editions of either Plus, Deluxe, Premier or Self-Employed then you will need to contact TurboTax support so they can push a 2016 desktop MAC installation file to your download account at no charge.
If you did not pay for one of the 2016 online editions then you will need to go to this TurboTax website to purchase a download (Windows or Mac) of the 2016 desktop editions - https://turbotax.intuit.com/personal-taxes/past-years-products/
Go to this website to contact TurboTax support during business hours - https://support.turbotax.intuit.com/contact/
Support can also be reached by messaging them on these pages https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax
