Oh I see! Yeah, you can’t do that. The only collision you can have on a character that interacts with the rest of the world is the one default capsule. You can try to create as many collision boxes and stuff, but none of them will work as in game collision due to how the character system is created.
A solution is to modify the C++ code or create a pawn class with custom collision. Watch this and it will answer some of your questions: Quadrate - How I Made A Game In 2 Days - YouTube