Run the tomcat server and specify external config file using axelor.config java property

I am confused by the instructions. What does it mean when the instructions say:

run the tomcat server and specify external config file using axelor.config java property

What exactly should I be typing to start the tomcat service?

The command sudo su -c "/opt/tomcat/bin/catalina.sh run" tomcat should start the tomcat service
But in your case you need to add config file sudo su -c "JAVA_OPTS=-Daxelor.config=/opt/tomcat/application.properties /opt/tomcat/bin/catalina.sh run" tomcat