Just a quick question about a new kitten?

I got a new kitten yesterday. She is 2 months old and very wary of humans, i managed to get her to let me stroke her finally. I have another cat that is approximately 1year & 8 months who goes around hissing and will give me a kiss when the kitten isn't looking which is rather funny. I was just wondering how long will it take for the two cats to get on a little, and how long it will take for the kitten to get used to humans, also i was wondering why she constantly meows, she has food water, litter tray toys bed etc..