To house train a pet rabbit, you can start by setting up a litter box in their enclosure. Place some hay or paper-based litter inside the box and encourage your rabbit to use it by placing some of their droppings in the box. Rabbits are naturally clean animals, so they will usually pick a corner of their enclosure to use as a bathroom. Keep the litter box clean by changing the litter regularly and consider spaying or neutering your rabbit, as this can help with litter box training. Patience and consistency are key when house training a pet rabbit.