For each web server in your cluster, you need to add it to the list of 'Back-end machines'. Each entry should be of the form host:port, where port is the web server control port that the web server listens on. The default value is 9089, although you may have entered a different value during installation. See the controlport setting in $ZEUSHOME/web/global.cfg to determine the current value of this setting. Cluster Settings
You need to make sure that the web server is configured to accept control directives from the admin server machine. On the web server, the file $ZEUSHOME/web/global.cfg contains a setting called controlallow. The default on a non-clustered installation is only to allow control settings from localhost. You should change that setting to also include the IP address of the admin server machine. Entering a value of all will allow control directives to be allowed from any IP address.
You also need to ensure that the backend webservers are using the same communication key file that the adminserver is using. The communication key is a shared-secret between the adminserver and the webservers, and provides added security. The adminserver communication key file lives at $ZEUSHOME/webadmin/conf/commkey, the webserver communication key file (if present) lives at $ZEUSHOME/web/etc/commkey.
Front-end machines are part of the Zeus Load Balancer add-on package, and are described in the Balancer package documentation.
If you are running any non-Zeus webservers as backends to a Zeus Load Balancer, then you must specify a control port value of '0' for each of the backend machines.