Can he go up the stairs yet? It's really just the reverse motion. My DD figured it out at daycare actually as they had a few carpet blocks stacked up on each other that she used to climb up and get stuck on. If you have something like that or can start at the bottom of your stairs, I would recommend that. Otherwise, you might just have to wait until he gets a little bit taller for him to learn. If you're worried, just make sure you have a gate at the top of the stairs that you keep closed.
