Select the parent object named hut_ in the Hierarchy and choose Component | Physics | Box Collider from the top menu. Your Box Collider will be created at the standard (1,1,1) Cube primitive scale, but we can use the collider editing feature and drag in the Scene view in order to resize and reposition it.
You will also note that it has been created with the center of the hut_model as its base; this is simply where the axes of this model were in the package it was created.
Ensure that you have the Hand Tool (you can quickly select it by pressing the Q key) selected as this hides the 3 axis handles for the object, making it easier to adjust the collider boundaries. Hold the Shift key and drag the boundary dots on the sides of the Box Collider in the Scene view until you have something that looks like the next screenshot:
Now, we will ensure that this is not an ordinary collider but a trigger! In the Inspector view for this object, check the Is Trigger checkbox on the Box Collider component.
Let's see now how to write code for managing triggered events.