Unless the units were rewired in the past just place them on the track. They should be in sync.
I have two (2) A unit locos. I want to make one of them into a B unit. I'm using DC. I think that all I have to do is reverse a couple of wires to get the units in sync . Am I correct with this assumption? If not, what do I have to do with what wires? Thanks ahead of time.