The spiritual blue print is the astral self. The physical body is the exact duplication of the mental karmic patterning of this blue print. Most people play out the life unconsciously following this pattern. By that I mean, creating little to no change in the direction of the mind.
To know what it says requires an attitude, and a belief that there is always the potential to change. One must have a willingness to train the mind to change the flow of its patterning, thereby increasing ones awareness of what is beyond ones preconceptions, ones conditioned concepts. It is easy to know, as you say, what it says, by watching what you think and do, pay attention, how do you react to others, to your life. Can you see your own prejudices? Are you able to see your own judgementalness? This is difficult for most people. What is your philosophies of life? Are you willing to accept the potentiality of other philosophies? It is most difficult if one is unable to philosophize about life.
How can you use it in your practice? Through constant reflection. Become more conscious of your unlimited potentials that are locked in your unconsciousness. Do not defend your concepts and your opinions. Simply try to transcend the limitations that they put in your life, this will make you one who is inclusive rather than exclusive.
Perhaps the blue print is merely a set of limitations that we have formed overtime. And through those mental forms we have taken the physical body in order to live out the desires that are within this mental form, the blue print. Truly, it is only ignorance that holds us in these binds. Remove it, remove the ignorance, desire to do so.
My blessing to you all