How to add custom collision to a Character class blueprint?

I have a character that’s much wider than the default capsule can cover. I tried setting the capsule’s preset to nocollision and putting in another box collision but the character kept falling through the floor. Am I missing an option somewhere?

Hi, You know that you can change the default shape of it. Or change the collision preset to Blockalldynamic

Change the default shape? How can I do it?