Step 1: Creating separate territories
Cats like to be the boss of their own territory. So we really recommend that you keep your kitten in a separate place the first time you bring them home. Give them their own safe place where they can eat, drink, relax, sleep, and go to the toilet. That way, there’s no immediate competition between your cats, and your new kitten has time to adjust to their new environment. So no seeing each other for the first few days.
Step 2: Getting familiar through scent & sound
Smell is very important to cats - it’s their main form of communication. So before meeting, it’s smart to help your cats get used to each other’s scent. You can do this by gently rubbing the same towel against both their cheeks. Or, if possible, switch their territories for a short time. Make sure they don’t see each other though!
Once the cats are used to each other’s smell, you can bring them closer by only having their territories separated by a door. That way, they can smell and hear each other. You could do this by giving them their meals on either side of that closed door. The positive association they have with food will only help to reinforce a positive association towards each other. When you feel like both cats are comfortable in each other’s presence, it’s time to go to the next step.
Step 3: Seeing each other
Ideally this step takes place before you actually let the cats into the same room. In this step, you want your cats to see each other but ideally still be separated by a transparent screen or a gate. Same tip as in step two: feed them on each side of the screen or gate. They’ll get even more used to each other, and keep building that positive association between food and their new friend.
Step 4: First real life meeting
The first real life meeting - aka the moment of truth. Pick a room in your house with spaces for your cat to climb onto. Ideally, have one person taking care of the kitten, and one looking after the other cat. It’s best to keep both cats occupied during the first meeting. Give them something to do, whether that’s play time or feeding time. And reward them for good behaviour.
What to do when it gets physical? Interfere. Seperate the cats and try again the next day. Keep repeating this until they feel comfortable in each other’s presence without hissing at each other.
Step 5: Give it time
The most important step: give it time! For some cats, it takes up to a year to actually like each other. And sometimes, they just won’t get along. But try not to worry, most cats do get along eventually - particularly if you go through these steps carefully and slowly.