Freedom is right. Cats ARE a whole nother story!!

You need to isolate the newbie in another room, especially when you're not home to supervise. Let her out while you are there and keep a squirt bottle handy. Rub both cats down with a rag and let the female smell the male's scent, and vice versa. It's probably going to take a week or so until they start feeling comfortable with each other. Since cats can be unpredictable, it could take a little more or a little less.

If you can, feed them side by side, as this will give them a positive experience. Cats can be bribed with food. They LOVE food!!!

Rule of Thumb: One litterbox per cat, so you'll need two.

Get lots toys so they have will have something in common.

Are these babies spayed/neutered? If not, you need to be careful as kittens CAN reproduce. Don't want an unwanted litter.