What Do I Need To Do When My Cat Has Her Kittens?

Be there for her with  a warm blanket and some clean cloths and hot water.  As the kittens are birthing, you can help mommy by wiping them but usually, she will instinctively to this on her own.  Cats will often go into dark small areas, like closets to give birth, the need to feel protected.  Some actually give birth in their littre boxes.  Just wait and see, I'm sure all will go well

For starters they need to stay with the mother for about 6 weeks to a month. Make sure the mother is comfortable and ave water and milk.  And food available for the mother to get to easily

If it's her first litter, it's scary. She will seem so distressed. If your really anxious, like me, and she allows you, you can stay close by. If she watches you closely and seems to cry at you, you can try stroking her, to comfort her. Do not try to help give birth, by pulling a baby. If she is weak, after the birth of a babe, and she allows you, you can pick the babe up and place near her head. She will instinctively begin to clean. If she does not, gently clear the skin covering the babes head. Usually hearing a cry will bring the mom to attention. Try not to handle unless you absolutely have to.

All of the previous answers are good advice. I will add a bit more. Make sure momma cat is being fed a good quality KITTEN food while she is nursing. This will give her extra calories to produce good milk for the kittens. When she starts into labor and starts pushing. Watch your clock. If she does not give birth within four hours, get her to a vet. Kittens should be born within an hour of each other, but usually less time between each birth. First litters may only have one or two kittens, but to know for sure, take momma cat to the vet for an x-ray so they can see exactly how many babies she has.