Introducing New Kitten to Resident Cats?

We have rescued 2 kittens from the local animal shelter over the past 2-3 years, both spayed/neutered. Nova, kind and lazily happy, will be 3 years old this upcoming Halloween. Juno, wild and adventurous, will be 2 this upcoming July. They have become accustomed to being king and queen of their castle. We only had a day or so of slight dislike of Juno from Nova when we brought her home. They have been best of friends since day two. We brought home a new girl kitten 5 days ago and Nova just looks at the kitten and walks away as if he doesn't care, but has made himself scarce. My neighbor tells me that he's over at her house nearly all day now with her cat. Juno on the other hand stays near the house looking through the sliding glass door, checking to see if the kitten is in a room before she enters it. She is down right nasty behavioral wise (hissing, long deep growling sounds, raising paws as if to hit or claw, runs to a door and screams to be let out if the kitten comes near).

But now I've reached the pulling of my own hair point. Juno, (the female) is now marking my furniture! She is furious, I just know it. I cannot re-home the kitten; the kids love little "Po". What can I do to make the transition easier for my older cats? Po is completely content here in the home and shows no signs of being afraid or mean towards the others, she is so sweet! What do I do?