If Calendar and Contacts Server is in use on the server cPanel, users can use the Calendar Delegation interface.
- Navigate to the Calendar Delegation interface within cPanel
- Select the username whose Calendars you would like to delegate
- Select username to have the Calendars delegated to
- Enable write access if this is required
- Click create to complete the process
if using an external calendar app, follow the instructions for that software to add a calendar
If you're using Roundcube you can follow the instructions in our documentation to add the calendar: