See upstream README file for configuration and usage instructions.
Almost all information from that file is relevant.  However, from
the section "INSTALLATION", only this is relevant:

  * Edit a file like e.g. /etc/request-tracker4/RT_SiteConfig.d/90-local.pm
    and add the line:

      Plugin('RTx::Calendar');

  * Clear your mason cache

      rm -rf /var/cache/request-tracker4/mason_data/obj

  * Restart your webserver

For the Base Configuration section, use this HomepageComponents setting. You
may need to adjust this if you've added any, it is a good idea to check
HomepageComponents in Admin -> Tools -> System Configuration (the addition is
to include MyCalendar).

  * Set($HomepageComponents, [qw(QuickCreate QueueList MyAdminQueues
        MyCalendar MySupportQueues MyReminders RefreshHomepage Dashboards
        SavedSearches FindUser MyAssets FindAsset)]);

 -- Andrew Ruthven <andrew@etc.gen.nz>  Sat, 05 Aug 2023 21:13:34 +1200