You'll know.....she act just like any other female. You'll see her trying to find a area to give birth....most likely a dark spot.

When she gets close to time to deliver, she will start her labor breathing like any other woman would. Just let her do her thing.

Most cats like to be left alone but keep a check on her. In most cases everything will go with out a problem. I have had to cut the cord before and clean the sack off a first kittens and once I had to help start the kitten breathing. But that was on a very young cat who I guess just didn't know what to do yet.

And don't worry if it takes awhile after a kitten in born before another one to come, sometimes it can be hours in between kittens. Other times one right after another.

About 6 weeks after the kittens are born.....make a vet app. Get her fixed. Don't wait to long she will go into heat again SOON and you could end up with more babies.

Good luck.