Help getting animals to get along!

-A❗

I have 2 cats (sisters) that I've had for about 6 months. I just got 2 new kittens (3 months old, 1 boy/1 girl) I've had them for about 5 days (around the cats for like 3). I need advice on them getting along.

I've tried them getting used to the smell, separating them, but in the same room. One cat/one kitten. One cat/two kittens, 2 cats/one kitten! I just want to give up,but I can't!