Slowly.
That’s how you introduce a new cat or kitten to your other pets.
Everyone needs time to adjust. You cannot bring a new cat or kitten home and expect everyone to be friends right away. There are many articles written on the subject. We advise keeping the new kitty in one room at first. Let everyone smell each other through the door. You can even feed on either side of the door. Then trade spaces for a bit so the current pets can go sniff around while the new kitty checks out more of your residence. Be sure to give everyone lots of love and attention!
With a slow introduction you have a much higher chance of everyone getting along more quickly than just tossing someone new into the mix.
https://resources.bestfriends.org/article/introducing-new-cat
https://www.jacksongalaxy.com/blog/the-dos-and-donts-of-introducing-cats/