Agree with Tara, also if you make sure he has his legs open rather than closed it won’t get stuck and come out the wrong way! Eventually he’ll get it and push it the right direction himself x
Push his Willy down and remind him to do the same. Also make him sit quite far back
I checked when he sat down that it was in the right direction and if it ever wasn't I put it in the right place and then after a bit he'd do it himself