Whenever you insert a JMenuBar into the design grid, it is populated with some default menus.
Default menus
To change the defaults (maybe to add icons or customize the language), double-click the menu bar to open the Menu Editor, edit the menus as needed and then choose "Save as default".

Items of default menus are defined by Action objects. RADi creates the following actions: newAction, openAction, saveAction, saveAsAction, cutAction, copyAction, pasteAction and helpAction.

Normally a JMenuBar is added to a JFrame/JInternalFrame/JDialog/JApplet with setJMenuBar(). The RADi runtime library will do this if the menubar is positioned in the first row of the design grid with no other components in that row.
(You should make the menu bar span all columns of the design grid and set its cell height to 0, else the size of the resulting JFrame/JInternalFrame/JDialog/JApplet will be different from the grid size.)
Menu bar and tool bar
See also:
    Internationalization about how to internationalize menu items.