I have 2 1099R forms from the same location due to a state withholding change. Do I just add them together or try to add the second one separately?

You mention "change" that leads me to believe you have a "Corrected 1099-R".  The "Corrected" box should be checked at the top of the form.  If so, the unchanged information will be the same as the original and only the changed boxes will be different.  Therefore you only need to enter one 1099-R; the corrected one.