Any ideas on how to keep my kitten inside?

I have a kitten that I adopted and she keeps trying to run outside. She is living with my parents until I can move into my new apartment. My mom lets our older two cats outside so she tries to join. The two older cats are of course huge male cats that can handle themselves. My kitten is an itty bitty little six lb girl with claw covers. I am afraid if she keeps running out she will get taken by a hawk or other animal. She will not be let out when we move but I need to find a way to train her to not go out now. Just trying to fight her on it, doesn't seem to work and I've also tried putting her on the little harnesses. She just rolls over and cries. Any ideas??