Hi.Well I think he means to make a parallel light as big as the scene you are making(actually as big as the caption of the camera viewed from top I think).Then you have to apply the caustic texture as gel(It can be downloaed from his site).Then edit your light.Apply 200 for lightness I think and 0 for softness as the scene will seem unrealistic with more softness.(I am not sure about this).Mark volume visible light and infinite light and linear fallof.Next is the editor for texture used as gel.Hope that I got it right ;)