Sundog,
Just put them together while they are a swarm. Bees from different hives that swarm at the same time in the same location will often combine. When they get to the new location the queens then fight it out and decide who will be the queen.
If one swarm is already established. Add a bunch of smoke and pour them in. I just had a swarm come from a different area and it moved into a nuc that had a very small swarm with a queen. Half of the bees went in that nuc and half went in another nuc that I got from the same location at the same time. I was glad to see they reinforced both of them. The next day I noticed only a couple of bees going into the smallest hive and I opened it up and they had moved out and probably moved into the other nuc. They had to walk past another hive to get to it.
Jim