How to replace film door?

Hello! I have one of these that I bought ages ago but dropped and it broke the pointy piece on the door that allows it to latch shut (so you can't lock the film door). I also bought another one for parts multiple years ago (I have a hard time getting around to projects hahaha) that has a good door but I don't really see how to remove and replace it. Anyone have any experience fixing these cameras? Thank you!