Install the plugin jar file in your hub server(s):
1.7.10-1.12.2   ServerSelectorX-Premium-2.1.0-legacy.jar
1.13.2+         ServerSelectorX-Premium-2.1.0.jar

Wiki: https://github.com/ServerSelectorX/ServerSelectorX/wiki

SSX-Connector sends server status and information to ServerSelectorX. Install it on all servers to send data to hub: https://github.com/ServerSelectorX/ServerSelectorX/wiki/Installing-SSX-Connector