Put a litter box in the corner of their cage with some feces and pee in it. If they have run of the house keep them confined to a small area until they are trained and gradually make it bigger. Put a hay rack beside or on top of the litter to encourage them to stay there. Most rabbits like to nibble when pooing. Pick up several times and day and place them in their dirt box. Choose a corner of the cage that they are already using as a toilet. Most rabbits will choose just one area. Good luck.