Well, there's a lot you can read about it. Basically, a portion of you is always existing in the Astral Plane as its a layer of reality, just as essential as any other. However, you can project your awareness into your Astral body and navigate through the Astral Plane... however, it takes practice to specifically focus on the Astral. In fact, every night you Astral Project but don't really have any memory of it - basically, what you practice is the ability to remember these experiences.. regardless, the work that is done there is necessary and beneficial regardless of whether or not you remember.