If you need to make changes to your return prior to filing your Returns
Log in to your TurboTax Online Account
From the Overview page
Click on My TurboTax
My Tax Timeline
In the Some things you can do area
Select Add a state
This will let you back into your Return to complete and File it.
However, if you have already filed the return, you will not be able to make changes to it. You will have to amend it.
You will be able to amend as soon as Form 1040X becomes available. At this time the expected date of availability for the form 1040X is
02/05/2020 , however that date is subject to change. You can track it's availability by going to the following link.
https://care-cdn.prodsupportsite.a.intuit.com/forms-availability/turbotax_fed_online_individual.html