To have the most success with introducing them, put the kitten in the bedroom and the cat in the living room - make sure they both have food, water, toys, a place to sleep and a litter box. Keep them separate for a few days until the kitten is adjusted to its new surroundings - you will know this when it is eating, drinking, peeing and pooping regularly, plus if it comes out of hiding (or doesn't hide) when you enter the room. By the way, because cats have such a stronger sense of smell than humans do, both of them will know the other one is there immediately.
Once the kitten is ready, the first thing to do is to switch them for about ten minutes - let the kitten explore and let your cat in the bedroom. You are getting them used to each other's scent. Do this a couple more times in the next couple of days.
It's then time to meet in person - the best way is to have one person hold each cat while being in the same room. Don't let them touch - keep them about six-eight feet away from each other. Do this for five-ten minutes - make sure both people involved to not look at the cats.
Assuming those visits go well, they can then meet in person, but supervised. If it goes well, let them be.
You can expect a little hissing, especially from your six-year old, throughout this process, and that is ok. But if it esclates (ears turned back, growling, prolonged hissing), you'll have to go slower with this.
Good luck.