Welcome to the forum Arcane Girl
What are the names of your two cats, and which is the kitten? How exciting to have taken on a new addition to your family.
They key to successful introductions is time and huge amounts pf patience, but this may be even more the case given that your kitten hasnt had a great deal of socialisation in those first few weeks of life.
My advice would be to try and clear out the room in which your kitten is staying for the time being, giving him no place to hide other than a bed, which could be in a cardboard box with the side cut away, or a proper cat/dog cage with a blanket draped over the top. If you can, furnish the room with a clean litter tray, a scratching post and platform, some toys to play with, and clean food and water bowls.
Two approaches. Whilst he's in his room, coax him out of the bed area with toys and play - Da Bird or a Flying Frenzy toy will be just the thing to tempt him out, but if you don't have anything like a fishing rod style toy, you can tie a piece of string round a scrumpled up piece of paper and use that instead. Use it like "prey" have it swoop, and wiggle and scurry along the ground, twitch and flip. It may take a little while for him to show interest so you'll have to persevere.
If he wont participate, then just sit quietly on the floor in his room, and do something else, like read. Dont make direct eye contact, and wait to see if he ventures out. If he does, just let him explore without exerting any kind of pressure or making sudden moves. Once he has ventured out a little way, try putting a little kitten treat or a dreamie down at a midway point between you and him - make him work to get it. Once he's taken the bait as it were, you can lay a little trail from his roosting place to where you sit, and wait to see if he comes out. Try petting with a closed fist - it's less scary to cats generally than a grabby hand.
Also, try leaving something with your scent on it in his room when you're not in it with him. You could also try scent swapping, where you leave something with your older cat's scent on it in his room, and leave something with the kitten's scent on it elsewhere for the older cat to scent track. Socks and nightwear are good things to use for this - rub them all over the cats, especially round their faces, ears and chin to get the scent on, and then exchange.
If all of this bears fruit, you can either leave the door open for him and see if he ventures out of the room, or you can bring him out for supervised introductions, depending on how your other cat reacts, and whether the little feller will let you pick him up without too much stress.
If your other cat shows no signs of aggression or hostility, then you can see if you can just let them explore the mutual space a little - your older cat may wish to investigate the place where newcomer kitty has been holed up, cos no doubt it will be very interesting and full of unusual scents.
(How did that get there......?)
See if you can engage them both in a joint play session - sometimes seeing another cat play will pique the newcomer's interest and vice versa, but monitor this carefully to make sure neither gets too boisterous or frightened by the other's. Around half an hour at a time should be enough at first, and if you can repeat this three or four times a day it will soon have the effect of getting them used to each other. If hostility's apparent, then remove the kitten back to his bedroom. Make a fuss of both the newcomer and your existing cat equally, as existing cat may feel pushed out.
Getting a plug in, such as Feliway or Pet Remedy can help to keep both cats calm, too. We put one upstairs on the landing and one in our living room when we were introducing Tinks and Moray, but neither of them were particularly timid, more just wary.
I hope this will give you some ideas to try, but if not there are some really good threads on here regarding cat introductions, so have a good look. Am sure there will be other suggestions very shortly. Also check out the stickies for the Jackson Galaxy clips, and have a look at his website for further ideas.
http://jacksongalaxy.com/Another good place to try is The Way of Cats
http://www.wayofcats.com/blog/We'd love to know how things go - and to see some piccies of your babies if you're able to post any.
