If you have a pet carrier, keep it inside temporarily for
safety. Have fresh water available. you'll have to clean up after
it pee or poo.
Check its mouth for teeth. If there's teeth, it can eat moist soft
cat food. If no teeth yet, can buy formulated milk for kittens and
pups, not milk for human consumption. If it's too young, you'll
need a milk botlle for kittens. Buy the stuff from pet shops.
A kitten need to be fed up to 5 times a day.
If you intend to keep it, bring it to a vet for check up. Google
for information. A lot of cat and kitten information there.
Don't dump it. It will die without its mother or human
intervention. Send to SPCA and chances are it will be put to sleep.
Think about it.
I've had experience in bringing up a kitten. She's now four years
old.