In order to be able to perform this you must be able to stay in the horse riding stance for at least 2 minutes reasonably comfortably. If you have no previous training in kung fu you will need to practice the stance on its own for a month or to before moving on to the full exercise. To perform the horse stance begin standing upright with the feet about 1.5 shoulder widths apart; keeping the back bend your knees and straight lower yourself down until  your thighs are parallel to the floor, or as close to this as you can manage. Without bending the back or neck forwards, or straightening the legs, and keeping the breathing steady, concentrate your awareness on the Dan Tien, the energy storehouse of the body which is located within your abdomen about 3 inches below the level of the navel. Hold this stance. If you are new to this you will probably find that about 30 seconds is all you can manage. Practice regularlt until you can hold this stance for at least 2 minutes. This is a good chi kung practice on its own, building the energy stored within the Dan Tien. You can also add to its effectiveness by visualising a sphere of light at the Dan Tien, another in the centre of the chest, and another above the head, entering at the crown, and a column of light connecting them and descending to the ground between your feet, concentrating on holding the column, which is the central meridian, and the spheres on it in a straight line.