Not a cat expert but am a dog owner...
Syringe feeding? stroking throat to make it swallow? Progress to getting it to lick off finger? Put some on its paw to lick off? dunk its head in the milk?
Like I said, not an expert and I really think you should call a vet.
Keep it warm. How old is it? My mums friend kept her newborn kittens in the oven believe it or not!
Be cafeful though, as the mum cat sometimes eats weak young (happened to the same person) and I guess if you handle it too much it might get rejected because of your smell....
HTH, but like I said, call a vet.