as it is an orphan (i presume), it has no mother cat to learn
from....but not to worry, it will learn to do it (clean itself)
later as its animal instincts will guide it to all those practises
(self grooming, using the litter pan).
in the meantime, give it lots of attention with regular gentle
strokes, that would assure your kitten that it is being loved and
also give it some hints to imitate the action of self
grooming...
also, would advise you to surf the web or pick up some books on
keeping a kitten, it'll help a lot. 