So you've lost control over your Citadel Installation by revoking your own Admin priviliges, forgetting your administrator user's password, or some other reason.
The way out of this situation is to run the "setup" program (which will be in /usr/local/citadel/setup for Easy Install or /usr/lib/citadel-server/setup if you have the .deb packages), and enter a new or existing user name for which you know the password. The next time this user logs in, Administrator privileges will be granted.
Note that in case of running in Host Auth / LDAP mode you need to specify the user's display name, not their host username.