This documentation is not using the current rendering mechanism and will be deleted by December 31st, 2020. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.
You can create categories to structure event records in the frontend (e.g. show events which belong to one or more categories)
Since the extension uses TYPO3 system categories, you create new categories by choosing “System records” -> “Category”