Originally Answered: "Establish the context" in an argument meaning?
Context means the set of circumstances or facts that surround a particular event, situation, etc.
Ask yourself what is the who, what, why, where, or how of your particular point. Is it drug use in minority populations? In popular culture? In the 1960's? In Brooklyn, New York?
Is it how it relates to their upbringing? Their performance in school? Marital status of their parents? Their likelihood to be incarcerated? Is it stuff you can get over the counter (inhalants, cough syrup)? Is it illicit prescription drug use?
Likely, you will be stating that two things are causal or not and provide evidence to support your position. For example, "Veiled references to drug use in popular music in the 60's by bands such as the Rolling Stones, the Doors, and The Beetles, gave rise to a widespread increase in teenage drug use. (By the way, I just made that up, I'm not saying it is true.) Then you would add your evidence that there are veiled references in the lyrics and that drug use increased. You might also add other context that affects your argument, such as the fact that teenagers were swept up in mass protests of the Vietnam war and also groups in which they were exposed to and freely shared experiences (music), possessions (such as drugs) and ideas (such as alternate mental states).