Yes, you can add the 3rd state on your return. If you lived in multiple states and earned income from each state in 2017. Normally, you would file part-year return for each state. Depending on the state you were living, some states does not require a state tax return.
Here are the steps to add an additional state on your return.
- Start from Tax Home page of your TurboTax online
- Click on Take me to my return
- Click on the left side State tab
- Click on Continue
- At the bottom left, click on Add Another State (see attached screenshot page file)