
Basically you just leave them to it but make sure to spoil the adult cat extra. Avoid having the kitten on your knee when the adult is around -that actually helps a lot. Cats are funny and need to know they are still number one. Spend time with the kitten when the adult has its back turned, so to speak. :) It can take a couple of weeks, but most will accept a kitten eventually, whether it is just a grudging acceptance, or if they actually like them. A 9 months old cat is adult, but only JUST adult, so should find it pretty easy to accept a newcomer. :)
The one thing I'd be a bit wary of here though is that the kitten is so extremely young. :( 7 weeks, that's awful, that kitten should have stayed with its mum for another 6 weeks, so the risk is that the kitten may try to suckle the adult cat whether it is male or female. It won't be anywhere near fully weaned yet so will go for anything it thinks it can suckle off.