What do i do when my fish gives birth?

ok my cousin( j.r he is 7) has a fish tank filled with fish, yet im not sure what type of fish. he is away for the summer in colombia so for a while im taking care of them, 2, of 1 type of fish, is pregnant. 1 of them is about to give birth and i don't know what to do when it does. of course i put it in a different fish tank but then what do i remove the mother before she eats them or take out the baby's or feed them as soon as they come out i need step by step instruction. some one help as soon as possible i need to know what to buy for the baby's cause i have 2 pregnant fish please help as soon as possible.