Step one:
Open the picture that you want to light. Create a new layer and fill it with 100% black.

Step two:
Press "M" to load the Marquee tool and make a selection (Round or Rectangular)

Step three:
Apply the Plastic Wrap filter (Filter/Artistic/Plastic Wrap) and change the values as you like.

Step four:
Goto the Layers palette and change the Lens layer blending mode to Screen. Your Layers palette should look something like that.

Step five:
Now all that left to do is it to take the Move tool (or press “V”) and move the light layer to the place you want it to be.