First, give your bunny a day or two to heal and relax before trying any kind of training. Make sure to examine his neutering scars once a day to make sure they are healing properly for the next few days. Once you are ready to start litter training, make sure not to give him too much freedom at once. Give him a limited amount of running space, and if he poops anywhere outside the box, make sure to put it back into the box (do not throw it away, but put it in the box). Also, I’m not sure how often you clean the bunny cage, but for the next few weeks become an INSANE bunny cage cleaner! Check a few times a day – any time there is poops outside the box, put them in it, any time there is pee outside the box, clean it up with vinegar to get rid of the smell. Even if there are no pees on the floor, give it a clean with vinegar often. In contrast, only clean the litterbox every other day or every three days. This will help the bunny understand where the pee and poos go, and where they do NOT go!