If you have not filed your return or if your return has been rejected you can add a state by taking the steps below.
1) Sign into TurboTax Online
2) Continue your return by click Taxes > Tax Timeline > Take me to my return.
3) Click on the Federal Taxes tab (Personal using Self-Employed w/ Business Tab)
4) Click on Wages and Income (Personal Income using Self-Employed w/ Business Tab)
5) Click Jump to full list
6) On Wages and Salaries, click Start/Revisit
7) On the W-2 Summary Screen click +Add a W-2.
If you have already filed your return and it has been accepted you will need to amend your tax return. Please see the following FAQ article for instructions. https://ttlc.intuit.com/replies/3288565