I have received 4 separate W2s from the same employer, where box 15 is different in each separate w2

[JamesG1]

You likely have received one IRS form W-2 with the income reported to a variety of states.

In most cases, the total of all of the box 16's will total box 1 income.

If this is the case, report the one W-2 box 1 through box 14.

Report each of the multiple state taxes boxes 15 through 17 as they are listed.

[SteamTrain]

TTX will allow you to enter new lines for each of the states for boxes 15,16,17........all on the same W-2 form.

IF the main Federal W-2 has a state line listing as "Total State"  you ignore that  one, and just use the state listings in the extra State W-2 forms the employer provided.   SO you might have just 3 states to enter for 3 separate lines for boxes 15,16,17......or 4 states, if there actually are 4 states listed.