Well I had the same problem, only with rats. So...I had two seperate cages and brought them closer together over time. Once they are very close for a while, try putting one into the other cage, and see if they react. Of they respond positively, then keep them together longer. If they respond negitively, move the cages further apart and then start moving them closer overtime again, and do the same thing. Soon they will get used to each other. Also to speed things up, you can even bring them together earlier and see how they react. It takes time.
I hope this helps!