How To Make Pre-made Models Collide?

So i got several models of the asset store, specifically a character with premade animations and some low poly trees and such. I got the character to move around, but he walks right through the fences and trees! I already tried adding a rigidbody on the player, but that didn’t help. Does anybody know what to do?

add a mesh collider, idiot

Probably a silly attempt at an answer…but have you placed colliders on your game objects?