What do I do if box 15 on my W2 has two states?

[AnnetteB]

You will enter both rows of state information on the same W-2 form.

If you are using TurboTax online, this is accomplished by clicking the blue + Add Another Row link shown directly under box 15.  Click on the picture below for a visual reference.

If you are using a CD/downloaded version of TurboTax, additional rows automatically appear as you fill in the ones already displayed on the screen.