Change cover in Documentary Series

I would like to change the cover of a series of documentaries, specifically Planet Eart II, to the application choose a cover that is not to my liking and would like to change it to another. I have tried in the following way:
From the documentary root and does not take the image of jpg that I have copied.
Planet Earth II.s01.e01.mkv
Planet Earth II.s01.e02.mkv
Planet Earth II.s01.e03.mkv etc …
Planet Earth II.jpg

Apart I have also tried to create a folder:
Planet Earth II (folder)
Planet Earth II.s01.e01.mkv
Planet Earth II.s01.e02.mkv
Planet Earth II.s01.e03.mkv etc …
Planet Earth II.jpg
Folder.jpg

I would like to know how I can change the image of a series of documentaries, since you have to bear in mind that each chapter has a different name, and what I want is to change the cover of the series, not the chapters.

Overriding series and season artwork is possible. It is done a bit differently than movies as it requires items to be organized into folders in a specific way.

A bit more info on how this works can be found here.