Each one has a personality so it's random. Our introduction took 4 days. 2 with cages side by side, 2 with them loose in the bathroom together, and then I put them in the cage. A couple tufts of fur were pulled but the rules were quickly set and next thing I know they are using each other as pillows. On the other hand some people have spent months at it. There's no intro faq here so we just kind of winged it and got lucky to have a pair that just ignored each other at every step. Start with a cage next to a cage or a cage in a cage (make sure they can't bite each others' feet) and watch how they act. When they are not all excited, upset, or otherwise making a big deal out of the other chin then you can move to the next step. Some never will get along.