As long as you have not e-filed or mailed out your tax return, you can get back into your return to make changes by following the instructions below. You do not want to Amend your return.
- In TurboTax Online, sign into your account.
- Select Tax Home in the left menu.
- Scroll down to Your tax returns & documents.
- Select 2018, and then select Add a State (you're not actually adding a state, this just gets you into the right menu).
You can now go to the menu and and make any necessary changes needed.