I will tell you the true, beeing a trader is a long hard way, i studied many courses about harmonics and still practicing and testing. It is not just simply reading and then profiting from the market. Having said that you can start with Harmonic Trading Vol 1 by Scott Carney.
don't want to step on anyone's toes, but I teach harmonics in my Trading program. Here is a cheat sheet to start with some popular patterns (https://drive.google.com/file/d/0B0tsvqiJUFB1STdRM2NpVFB6VXc/view?usp=sharing)....enjoy