Since you did not file a 2018 return, then you would put zero for your 2018 AGI.
Where do I correct my 2018 AGI in TurboTax Online?
To revisit the 2018 AGI section in TurboTax Online:
- Sign in and open your return, if you haven't already done so.
- From the left menu, select File (tap in the upper-left corner to expand the menu on mobile devices).
- Select Start next to Step 3 (if needed, revisit Steps 1 and/or 2 to activate Step 3).
- Select I want to e-file.
- Continue until you see the place to enter your 2018 AGI.
