To be able to use this menu item you need to have an Administrator Account and be logged into CCalendar as administrator.  Over the administration-menu item "Participants" you get to the overview of all your CCalendar participants (CCalendar-Accounts).  In this overview you can see all accounts for your organisation account with name, account name, type of account (admin / user / guest), their e-mail address as well as their subscribed appointment groups.

To create a new participant, click in the overview on either "Create new participant" or the New-symbol on the top right.
To edit the individual settings and rights for an existing participant click on the pencil-symbol at the right edge of the corresponding participant.
To delete an existing participant click on the delete-symbol at the right edge of the corresponding participant and confirm the security query with "OK".