hello i am quite new to unity. I am making a game and have imported a house which is a .fbx file, with over 200 different objects inside of it (including walls). my question is how can I get the default character 3rd person, to collide with it??? please help!
First, if you have over 200 different objects in it, that is a bit of an issue in itself. Try to combine those objects in your modeling program. Second, when you import an FBX there are import options with a checkbox asking if you want to generate colliders. Just check that off and hit apply. You should also consider what actually needs colliders and what does not. If something is not reachable by the player, then there is no need to add a collider to it.
If you want to do it the long way (but probably best way) select each child of your model then go to the TOP of the screen, go to Component / Physics / Mesh Collider. That will make it work. Then make sure you have added a collider to your player model, too.