So we have to go back to the first material when I wrote RENDER IT. For the next thing we will work with this older values. Hopefully you make a copy of it ;). If not it would be a good idea to make the material again. Anyway, if you are done create a new light source and use the position parameters as well as the light parameters as shown below.
When done just render the scene again. If you still can, play around with position, color and so on. ;)