Would anyone please fill me in on what happens at the very beginning? I arrived at the part where the people in the club (if that is what it was) are being told to leave by the police, and then the vans start coming in to take them to the station.
You didn't miss very much. In fact I really don't think you missed anything. That scene was really there to open up the movie- telling us that police were harassing black people, even black service members back then. Then the stuff immediately after is when the protesting/rioting started.
I'm trying to go for an engaging, funny youtube channel so, if you have the time, take a look. Hope you enjoy what you see. Thanks in advance. A review of the movie here-https://youtu.be/uMrky7pGk5w