See this TurboTax support FAQ for completing a 2016 tax return originally started using the online editions - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...
If you are using the TurboTax 2016 desktop software installed on your personal computer then just complete the tax return. In the File section of the program choose the Mail option since a 2016 tax return can no longer be e-filed but must be printed and mailed.
There are no penalties for filing a tax return after the due date if the return is being filed with a tax refund or there are no taxes owed.
