How to create libraries with the Multi Library plugin?

I would like to be able to use different libraries for different purposes.
E.g. having a 'classical' and a 'non-classical' library.

It looks like the Multi Library plugin could be useful (necessary?) for this.
I downloaded and installed it, and then tried to find how to create these multi libraries.

There is a settings page, with options that are not completely clear to me.
Such as: "Library directory", which at mouse hover-over on the info button says: "Library directory".
Or "Library templates directory" that at mouse hover-over on the info button says: "Library templates directory".
Should I look for a specific location where some library, or library files are already present?
Or should I create some folders anywhere at will?

And most importantly, I can't find any clue or explanation on how to actually create libraries with this plugin.

Somebody to the rescue please?