Welcome to the forum, Carroll!

Thanks for joining and for hopping right into the discussion here. You will find that it is a friendly and helpful place.
Now, to your question: Mind Power - what is it, how does it work, what are the potentials?
Well, that would be a great topic for a book I think.

But I will try as quickly as I can to give a synopsis of how I see it:
First, the average person has no understanding of mind power at all. They operate from a place in which they are like a victim of their thoughts and emotions. When I think of mind power, I actually include in my understanding of this, control and focus of the emotions as well. Control the mind and you will control the emotions. The typical mental condition is one of thoughts rambling nearly aimlessly within the mind, running willy nilly here and there, and often repeating the same series of ramblings and obsessions over and over again each day.
The first step toward mind power is to focus the mind. This is the stage of concentration. We learn to achieve one-pointed concentration of the mind. This is best done through meditation, but actually many people in the world today are fairly adept at this through the focus of the mind in business applications, or in the creative arts such as writing, painting, dancing, sports, etc. These all provide a great focus of the mind, and these skilled people have developed a real power of concentration and will power.
Once you learn to achieve concentration, the next step is to lose yourself somewhat in the focus, the focus becomes so complete, that the normal mental chattering process will fall away, and you will experience moments or stretches of "in the flow" experience. This is written about quite a bit in sports psychology, but it occurs in all areas of endeavor. What we want to learn next is to achieve a state of relative stillness of the mind. The mind is to be our tool, it is like a focusing lens for manifestation from the higher causal planes. When you work in meditation to first concentrate the mind, then achieve stillness, through focusing the mind into these intutional planes of awareness we are then able to consciously focus this light through the lens of the mind. There is a science to all of this, related to meditation techniques.
The final step in mind power comes when you achieve relative purity of mind. This purity comes first through the concentrating and then the stilling processes. At some point you will begin to achieve a detachment of identification with the mental processes. You will realize how you have identified your sense of self with all of these thoughts, feelings and dramas. But you are not any of these things. When the ego begins to diminish its hold on the mind, your mind is beginning to become pure. The pure mind is the egoless mind. If there is no ego attaching to the thoughts that come into the mind, there is no impurity. From this state of pure mind, concentrated, then directed into the causal and intuitional planes, you truly gain "mind power", which is the ability to rapidly manifest your thoughts.
As far as the potential of this - at the full flowering of mind power, the manifestations will become so rapid that it defies understanding. Miraculous happenings of synchronicity will begin to string together from moment to moment.
There is so much more that could be said on this, but I hope that this gives you some idea of where I am coming from.
Best wishes,
Blake