Well there are two ways you can do it.
One has to do with shaders which I am not well versed at.
The other way is you could place a lamp and place your light marker so it appears that the lamp is illuminated.
Remember the light from the little light bulb marker comes from the top of the bulb.
When you place the bulb, click on it then pull up it's settings you can then use the arrow keys to position the light marker for best results.
Here is an example:
you might check this link out about directional lighting it's actually pretty easy, and can be really effective.
http://forum.thegamecreators.com/?m=forum_view&t=186793&b=21
IF you'd like shoot me an email and I can help you out with it.
