When introducing a new cat to an existing feline household, it is important to take things slowly and give the cats time to adjust to each other. Start by keeping the cats in separate rooms and allowing them to smell each other through the door. Once they seem comfortable, let them meet in a neutral space and provide plenty of toys and treats to keep them occupied. Gradually increase the amount of time they spend together, and be sure to provide plenty of love and attention to all of your cats.