How do I enter multiple states when entering my w2? I worked for the same company but in 3 different states.

Does your W-2 show the three different states?  If so, you can enter all of them in the section for state income taxes on the W-2.  The program will open another line as the first state income tax line is completed.

The program will show two lines for boxes 15-17. After you complete the 2nd state entry, and third row of boxes for 15-17 will just "magically" appear.

Here's a screen shot