The above answers are all correct... very good information. I will, however, give a suggestion for you to be able to see it.
Close your eyes and visualize the psi ball, keep going until its an intense visualization and you can feel the energy (be it heat, a tingling, pressure in your hand, whatever) and hold the visualization. Focus only on the energy ball until everything else is out of focus and very blurry. Slowly open your eyes but keep your focus on the energy and keep your vision of everything blurred (it might help to squint your eyes).
What this exercise does is train your brain to be able to bring your vision with you out of your minds eye and blend it with your regular vision. It may take some practice but its basically the same thing as day dreaming but you control the vision and can build and work with energy. If you practice a lot your brain (and third eye) may be able to pick up the very subtle variances of energies all around you when you open your mind to it.
Don't get frustrated if you can't blend them, most people can't and stress and frustration only makes it worse. If you can FEEL the energy then you are doing great.
I hope this helped.