Note: If you did not select the "fullblown example" (see DocUsingInstaller) then you will have to setup the login module properly before you will be able to follow this explanation.

After installing the "fullblown example" with the packaged Installer you can visit the www subdirectory in the WebBuilder2 directory. 
Move your mouse to the top of the browser window. A dropdown should appear with several links you can click on. Click on "Login" to be taken to the login form. In the login form you must specify a valid username and password for an activated user account. If you used the installer then you will have setup a superadmin account that you can use here.

Once you are logged in you will be able to see this by moving your mouse again to the top of the browser window. There you should see the username which you used during the login. If you have sufficient access rights you will likely see additional links/buttons now beyond a "logout".