If you draw a proper diagram, then it is self-explanatory. In this diagram, you have the glide path line at a slope of 3 degrees. One end of this line is the numbers on the runway, the other end is the airplane. At the aiplane end of line draw two more lines: the longitudinal axis of the airplane and a horizontal line. The angle between the horizontal line and the glide path is 3 degrees as advertised earlier. The angle between the horizontal line and the longitudinal axis of the airplan will be the pitch angle of the airplane at final approach, and let's assume it is 2.5 degrees. Thus the angle between the glide path and the airplane longitudinal line will be 3 + 2.5 = 5.5 degrees. And this is the angle you need to have the landing light down (relative to the airplane longitudinal line) to reach the numbers on the runway.