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...
Or download the PDF of the return and print, sign and date the return for mailing since a 2016 tax return cannot be e-filed.
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/print return (PDF)