When it comes to cats and introducing them to another cat that will be living with you the best thing that you can do is let the cats work out their differences in their own way. When it comes to cats there is always a hierarchy and when the new cat comes to the house they have to learn that they aren’t on top anymore. The best way to let this happen is to introduce them slowly to one another at first making sure that there are separate spaces they can get to to get away from each other. Allowing them to fight is another way to get them used to each other because not all fighting is bad fighting. Play fighting is a way to show who is incharge and to help develop a bond while showing the new cat who is in charge. Do not let your cats fight if they are hissing at each other or howling. Another sign that it isn’t time to fight is if their ears are down and their hair is standing up. In the end it just takes time, and for you to allow them to interact without breaking them up unless it is extremely necessary.