This seems to be a very old thread, but even so here is my view. PVM analysis isn't really much more than a series of reasonably basic mathematical equations, but some of them aren't necessarily easy to follow because the concepts, especially "Mix" which combines some concepts together and can feel a bit sticky to walk through.
There is a lot of things online, but I have found this YT tutorial the most easy to understand of all the ones I watched recently:
It's clear and well paced, and the way the equations work is well explained. Others I have watched talk too fast and they over complicate their equations. I have observed that different authors construct their equations in slightly different ways, but they reach the same answer.
If you have your data already, then all you need to do it slowly build the equations using the guide. I thoroughly recommend if you employ the autocalendar within your Qlik Sense Load Script it makes the delimitation of periods much easier as you are readily able to access things like [date.autocalendar.YearsAgo] etc.
The video above focuses on Price, Volume and Mix only. But I strongly recommend also building in "new" and "discontinued" data outcomes into your data solution because trying to correctly interpret the results using just Price, Volume and Mix can be very difficult when you have "new" and "discontinued" outcomes that should be considered in isolation.
I found working the formulas using a mix of variables and master measures the easiest.
My overall advice is start in Excel, grasp the concepts, then work in Qlik Sense.