creating active objects or spots otherwise said HotSpots

You would create hotspots by attaching Colliders to the objects you want to be clickable.

Then use the Camera.ScreenPointToRay function to send a ray out where the user clicked and check if it hit one of your colliders.

function Update () {
   if (Input.GetButtonDown ("Fire1")) {
      // Construct a ray from the current mouse coordinates
      var ray = Camera.main.ScreenPointToRay (Input.mousePosition);
      if (Physics.Raycast (ray)) {
          //Check which object was hit and do something
      }
   }
}