Do you have a specific area in his outdoor space and cage that he can use~ with whatever litter you are using (shavings etc.)?
I find that all my rabbits use the same spots over and over and once I know their preferred spots, I make sure that is where I put the shavings.
Even with adult rabbits that are new to me, if i watch a day or two, it becomes apparent where they 'go'.
Chances are the bunny will still poop everywhere if he has a large space, but once you see where he pees, put a litter box there and a few wet hsavings or pellets of poop and he should get the idea pretty quickly.