This kitten is far to small to be seperated from it's mother. If you know where the mother is, try to give it back. I have recently met a few people who have deliberately removed 1-2 week old kittens from their mothers because they wanted to have them as babies. This is cruel and unlikely to produce a healthy or happy adult cat.
If the kitten is abandoned or orphaned, you will have to do your best to offer comfort and security.