The MODX installer should install the package automatically from the modmore repository.
A custom manager page called Agenda is installed within the Extras menu. Also some snippets in the element category named Agenda are created.
There are some system settings available in the namespace agenda. These could also be edited in the settings (gear icon) tab of the Agenda custom manager page.
If you want to connect events, categories, calendars or locations to MODX resources, you have to enter the parents of those resources in the system settings.
To use the map and the geolocation option in the location address tab, you have
to enter a Google Maps API
the Agenda system setting
the Geocoding API in the created Google Cloud Platform project.
After the installation you have to setup a cronjob, if you want to use more than 100 repeats of a recurring event or if you want to setup feeds.