CalDAV clients can directly access the internal calendars (and task lists) of Kronolith. External calendars like events provided by other applications or remote calendars are not provided to CalDAV clients.
How to configure access to the calendars and which CalDAV URLs to use depends on the client. Below are a few examples on how to access CalDAV resources from common calendar clients:
Lightning, the calendar add-on to Thunderbird, requires to subscribe to each CalDAV calendar individually. In the "File" menu choose "New", then "Calendar". In the following dialogs choose "On the Network", then "CalDAV". Copy the "CalDAV Subscription URL" from the "Subscription" tab of Kronolith's calendar dialog into the "Location" field.
CalDAV servers can be added in the "Preferences" dialog, at the "Accounts" tab. Click on the "+" button and choose "CalDAV" as the "Account Type" in the upcoming dialog. Enter your user name and password into the correct fields. Copy the "CalDAV Account URL" from the "Subscription" tab of Kronolith's calendar dialog into iCal's "Server Address" field.
Evolution requires to subscribe to each CalDAV calendar individually. In the "File" menu choose "New", then "Calendar". Choose "CalDAV" as the "Type" in the upcoming dialog. Copy the server name of the "CalDAV Subscription URL" from the "Subscription" tab of Kronolith's calendar dialog into the "Server" field. Copy the path of the URL to the "Path" field. E.g. if your Subscription URL is "http://www.example.com/rpc/calendars/user/calendar:xyz/", then copy "www.example.com" to the "Server" field and "/rpc/calendars/user/calendar:xyz/" to the path field.