If you've already filed your return you cannot add a state. This may change your federal and state returns. So if you filed your return and need to add additional information, then you will have to prepare an amended return in TurboTax.
If you used TurboTax Online, simply log in to your account and select Amend a return that was filed and accepted.
If you used our CD/download product, sign back into your return and select “Amend a filed return.” You must file a separate Form 1040X for each tax return you are amending.
Amend ONLINE OR Amend CD/Download Amend 2016 - 2019