From what I take away from this, John Boyega's character is a part of the imperial army who crashes on Daisy Ridley's character's planet. At some point they adventure into the millennium falcon and harrison ford tells them everything they know about the previous events is true and then the rest of the movie happens
also it seems at some point John Boyega is either going to be discovered to be force sensitive or he's just gonna pick up a lightsaber just cause