creating active objects or spots otherwise said HotSpots

As you can see in the development I have attached below, I have areas where users will click on to activate services lik skype, facebook etc I read somewhere about doing just that but I cannot find back where in the doc it is mentioned? Can somebody help me with this? Thanks yves

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