The Server Manager is where all the work starts. In order to work with Database Workbench, you first need to register a server in the Server Manager. After registering, you will find many tools and options in context sensitive menus of the server.
The "Show Server Manager" button
After registering several servers and arranging them in folders, it could look like the one below.
Server Manager with several servers and databases
To work with a database/schema, you have to connect to it (establish a session) - this will open the Database Navigator - your source for working with database objects, viewing dependencies and much more.
Here are the steps to take:
After completing these steps, you're ready to start using Database Workbench.