How do I obtain my 2016 AGI?

To access your current or prior year online 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 View adjusted gross income (AGI)

You can also get free transcripts of your federal return from the IRS - http://www.irs.gov/Individuals/Get-Transcript

Are you trying to efile a 2017 return?  You cannot do that now.