If you are using the jBPM installer, this properties file is going to be in $jbpm-installer-dir/conf. If you are not using the installer it should be in $gwt-console-server.war/WEB-INF/classes
You can also set a system property via code or pass it on AS startup via -Djbpm.console.directory=XYZ where XYZ is the location of your directory containing process assets.
Hope this helps.