Need some help with auth tokens [TwitchLib]

That page was about the first thing I saw when I started doing research on how to do this and it means nothing to me. As far as I can tell it discusses http requests of some kind without providing any context about what the hell is going on. It’s seems like a reference material for people who know exactly how the system works and need specific details on a given step, it’s not “explaining these tokens to me like I was a mentally challenged child”.
It also offers no explanations on why the tokens used ended up producing a an exception regarding the scopes.
The broadcaster_id thing is a valid point. I looked high and low trying to find a separate broadcaster_id associated with my account, but couldn’t find it, so I figured I’d just try the username instead. How do I get the broadcaster_id?