I've heard two things about ringworm. One, is that it's highly contagious and that anyone touching it will get it. Two, and this from a vet, and also from one of my old tech school teachers regarding skin diseases as it relates to cosmetology.. was that it's highly contagious *except* that you're only really likely to catch it if your immune system or skin is compromised in some way. For instance, if you're handling the cat and your skin is scratched, or say if the person was HIV positive, etc... then it's possible that you would contract it, or rather it's a lot more likely.
That being said, I've dealt with several cases of ringworm with different cats, and one did not have any other cats around it, but we all pet it, and I was the one to medicate it daily, and had even touched the wound before we started medicating it, and I never contracted it and neither did any of the other office mates.
The last case was one of my current cats had it, and she was not quarrantined from the others, and they never contracted it, nor did any of us for medicating it.
So, in my experience, it's more likely that you catch it when you're system is compromised in some way, as I haven't ever gotten it even though I've dealt with it a few times.
Now, that being said, if you still want to keep the kitten quarantined, it's a good idea to go in and spend time with him. I'd spend quite a bit of time in there, but you may use the time for getting them used to one another. If he's been in there a few days, then take a sock, rub it over your first cat, and put it in the room of the newcomer.. make sure you get the face, particularly the mouth and cheek area. Put it in the room with the newbie, so he can get used to scent of the resident. Do the same with the newbie and put the sock from him out on the floor somewhere with your resident cat.
If you're going to keep him quarantined for a few weeks, I'd see if it were possible to move him into a larger room, especially if you can put him in a bedroom where he's got interaction with humans. You don't want to put him in the resident cat's territory or disrupt the normal routine of the resident, as this will stress him, but, this is a prime time for bonding with the new guy and you surely don't want to leave him all by himself for that time period.
Personally, if he gets along with the resident...I'd let him out. I know that there will be a lot of dispute on that opinion, but like I said, I've never had an issue with it spreading, and it seems to kill the virus pretty quickly once you start medicating. That's just my view on it, and it's not the response that most will give you, or even that most vets will give you, but.. I'm not very conventional and I don't always think that the popular opinion or advice is the best.
Ringworm is a lot easier to treat if your other cat catches it, or if you catch it than trying to bond with your kitten or repair emotional stress after the damage is done. This is a prime socialization period for the kitten, and usually this time is spent with it's mom and siblings learning how to interact.
My sister also just suggested something, and you may try it.. if you can put your other cat up for a bit, and let the kitten out, it can start socializing with the humans and start getting used to the house. It will also leave his scent behind for the resident cat to start to get used to. This would avoid direct contact between the two cats, although honestly, you probably wouldn't have to worry about that anyway, since they're most likely not going to be best buddies right off. They may be, you can never tell for sure, but.. it doesn't usually work that way.
I hope everything works for you and your little ones! Congrats on the new addition to the family! (And, we'd like to see pictures!!). Oh, and Welcome to TCS!!