What skills should I have to study psychology & I like to study about the boxy language & behaviors (under what category it is placed)?

Undergrad degree. In Psychology is probably what you are talking about. In addition to the general courses and college student would take you will need to take courses in research, statistics, general psychology, abnormal developmental psychology, and the like. If you eventually intend to become a psychologist you will need a doctoral degree plus several years of supervised experience and exams. See APA.org.
Informal? The skills are good reading comprehension and judgement. Find well-documented sources, not fads. Social psychology and communications is an area for body language. I never heard of boxy language. Best!