Logan's advice is right on target. Let them sniff to get used to each other, then let them have as much "face time" as they will tolerate. Seperate them if needed, then try again, but eventually let them "have at it" like Logan says, because that is the only way they will learn to coexist. If it seems like one will do harm, seperate them while you are not home or cannot closely supervise, otherwise let them get used to each other while you can supervise.