I really don't understand DUB

[WhatMeWorry]

I've been using DUB for several years and I've gotten it to work 
generally.  But I've been trying to troubleshoot a DUB issue for 
two days now and I've come to the conclusion, I don't really 
understand DUB and I'm tired of muddling through.  (Surely it 
hurts that I've never been exposed to a library or package 
manager in general)   Now, I've studied the on-line documentation 
and even walked through the code somewhat but I'm not making an 
headway.

Maybe a higher level approach is required. Is there some good 
beginner tutorial that I'm missing?   Ideally, like a gentle walk 
through, for both Windows and POSIX?