For a kitten this young you need to stimulate the kitten to poop and pee,This is very important to do and if you do not do this the kitten is at risk of dying.
from the linked site:
It is necessary to stimulate kittens of less than two weeks old to urinate and defecate as they cannot do this without stimulation from the mother cat. The ‘voiding reflex’ by which urine and faeces are released, is normally initiated by the mother licking the kitten’s ano–genital region (the area under the tail). Where the mother is not available, urination and defecation must be maintained by the human carer for approximately four weeks or until the kitten is independent.
You need to read all the information on the linked page or do a search on the net for hand rearing a kitten(in case the link dies).