Your Article categories Module displays a list of categories from one or more parent categories.
A note of caution: when setting this up this module you need to pay attention to two similar words:
When you want to try something such as a new module, set the access level to "Special", publish the module on a specific page of your website, and then log-in to the front-end of your website, navigate to the page where you published the module (in this case) and you will see the Module but no-one else will see it.
If/when you are happy, set the access level to, for example Public where everyone will see it.
In Joomla version 3.10.x Modules are created and managed via the administrator area menu 'Extensions' tab.
If you need a little more information you might like to visit Get Help with Article Categories Module.