The best way to introduce a new cat to a household with other cats is to do it gradually. Start by keeping the new cat in a separate room for a few days, and then gradually introduce them to the other cats in the household. Make sure to provide plenty of food, water, and toys for the new cat, and allow the cats to get used to each other's scent by exchanging bedding or rubbing against each other. Additionally, it is important to provide plenty of positive reinforcement and rewards when the cats interact with each other.