Which version of GWT / ME4S are you using?
If you are using GWT 2.2 or greater, you can start with the ScaffoldApp.java file and work through from there.
The architecture that is being used is the one promoted by Google that is MVP or Model View Presenter. It is powerful and elegant, but can be tricky to follow because it abstracts things that are often done in a more “direct” manner.
That class should serve up the list of top level places in the app, and each place is associated with one of your object types, etc.
Thanks,
Jack