Basically, this is what happened;
Lady Macbeth says she'll wait until Duncan goes to bed (he'll be tired) and she'll make sure to give the two guards enough wine to make them sleep heavily. That way Macbeth will be able to sneak past them to kill Duncan with the two guards' daggers. Then they'll place them with the sleeping. So practically, she must behave like a bandit, a pauper, a witch, etc.
hope it helps...
