This section in the book is really a preview of the macrocosmic orbit meditation in Fusion 3. When you get to Fusion 3 material, you will explore this more comprehensively; it can be skipped in the intervening time. The “version” of the macrocosmic orbit meditation given in the “Awaken Healing Energy” book is a simplified version, and is not really the complete picture.
The macrocosmic orbit opens up all 8 of the Eight Extraordinary Channels and the arms. In so doing, your whole body is filled with qi on a structural level. Also, as an added bonus, by incorporating the body, it strengthens your interface with the external world.
However, even after you learn the macrocosmic orbit in Fusion 3, the regular microcosmic orbit that just goes around the core still remains useful and important. The regular microcosmic orbit helps strengthen the core and lays the foundation for deep internal work.
In other words, you don’t need to add in the arms and legs now (unless you want). You can wait on it until you cover the macrocosmic orbit in full detail in Fusion 3.
When I first learned the MO, which I did through “Awaken Healing Energy,” I used to throw in a few arm and leg orbits during the course of a sitting. I discontinued it after a while, as I moved on to other practices and did not sit as long.