Well, all too few people actually teach this. The best way of learning it from personal experience is to teach yourself. Learn through mistakes, trial and error. Psionics is a practice of specified energy manipulation, it includes countless techniques, countless exercises etc... in this case, figuring things out by your own self given studies is the best way to go with it. Truthfully, having a teacher for such a broad category of "magick" will take even longer than learning psionics on average.
P.s the practice isn't easily used for offense. Psionic abilities are very difficult to build up enough power to do so much less control them; it takes years.