Hello,
We don’t have a special post with a description of the filters widget area.
Could you, please, provide us with WP Dashboard access to your site to check why the filters button does not work for you? It should open the additional area that displays filter widgets that you add to the Appearance > Widgets > Shop filters sidebar.
Also, you can manage the number of columns and some other settings of the filters area in Theme Options > Shop page filters.
Regards