How to get cats to get along?

I have the same problem at the moment. I adopted a stray kitten that I found on a pavement. The kitten is thriving now, getting stronger and playing a lot but my other cat really hates it. I separate them with closed doors when I'm sleeping or not at home, but supervise them when I'm with them. What I also do is I teach the little one not to go into the other one's sleeping territory, which is the backrooms of the house.