To get back into TurboTax to make changes, first log in to your account.
At the Welcome Home screen, choose Visit My Tax Timeline
Under Some Things You Can Do, at the bottom of the screen, Choose Add a State (you aren't really adding a State, but you will be able to access your return).
Once you are back in your 2016 return, you can make the changes that you need, and reprint the corrected return..
As long as you haven't already mailed your 2016 paper return, you can switch to e-filing method.