To learn the principles means to understand the basic rules or ideas behind something. It is about gaining knowledge and comprehension of the main concepts or guidelines that guide a certain subject or topic. Full definition
They occur because a candidate hasn't learned the principles of good resume writing. (resume-now.com)
Proven classroom training experience, with the ability to react quickly to change, strong verbal / written communication and excellent presentation skills, with demonstrated knowledge of adult learning principles. (members.climber.com)
We must learn this principle in order to have a democratic society. (christianitytoday.com)