I noticed in the video that the instructor made several adjustments to the position of the ‘sun’ lamp in the scene, trying to get the effect he was looking for. But the position of the ‘sun’ is irrelevant, since it represents a point source of light at an infinite distance from the scene. The only useful adjustment is the direction of the sun’s light, achieved by rotation. Translating the light has no effect.
I only mention this since people might be confused that dragging the light around the scene would never seem to have any effect. You can verify this by dragging the ‘sun’ lamp below the chess board.