Prepare a clean cage so that it doesn't smell of any of the does to be introduced. Don't use any toys that retain smell such as wood or cardboard unless they are brand new (no mouse smell). Provide two nesting areas although if all goes well they are likely to only use one. Then put the does in the cage and observe for a while. They'll sniff each other and there may be a bit of squeaking, though with does this is usually submission not a reaction to injury. It would be unusual for them not to get on to the point where they have to be separated, but if you see blood then take out the agressor.