Note that the guide referes to TOMCAT_HOME as the Tomcat installation directory.
CATALINA_OPTS="$CATALINA_OPTS -javaagent:/path/to/plumbr.jar"

When everything went smoothly, you will see the following banner in the restarted JVM standard output and a new JVM appears in

* Plumbr (15.01.4138) is attached.                         *
*                                                          *
* Plumbr agent is connected to the Plumbr Server.          *
* Open up to follow its progress. *