This meditation is made to ensure you recharge your life force and simply to relax.
This involves a specific way of breathing by moving the Stomach instead of your chest. If you watch an infant on his back breathing during sleep you will find that his stomach goes up and down not his chest. However the ability to relax into this breathing habit gets reduced while we grow up. To relearn it, you can start by sitting on a chair straight with your feet apart and breath. While you breath-in push gently your stomach outward. At the beginning if may feel artificial but after few days it will start being a normal habit.
Now, for the energizing part, lay down without any pillow or anything to elevate your head, it is also advisable to cover your body. The cover of the body actually is advisable during any meditation. Because the relaxation opens up the pores of your skin and you may invite un-wanted energy or simply cold.
Now, make sure there is absolutely no noise (you can use ear-muff if you like), and envision the air going down while your stomach goes up (You can place your hands on your stomach to feel how it is going up and down), then envision the air leaving you while you breath out... that is it. If you find that you are so relaxed that you want to sleep, that is perfect but don't change position. Stay on your back with no pillow.
When the energy circulates the body very well, you will feel warm or hot air going into your stomach..you can't mistake that when it happens. So keep noticing for that and if it does happen, just remain relaxed and keep the same concentration on the breath..
Usually I do this after the end of working day, I start the breathing and sometimes I feel the hot air and then end up snoozing for about 5 minutes, I get up once the body is filled just like a battery being charged and ready to continue an active afternoon..