Gtk-WARNING** Atempting to add a widget with type..

["Algirdas Jarockis" <algirdas jarockis gmail com>]

Hi all,
im just starting with gktmm-2.4 and i have problem that i can not add drawing area object to window where menu is already added. The warning message at runtime: 
"Gtk-WARNING** Atempting to add a widget with type gtkmm__GtkDrawingArea to a gtkmm__GtkWindow, but as a GtkBin subclass a gtkmm__GtkWindow can only contain (...) it already contains a widget of type gtkmm__GtkVBox"

Source of adding menus is from tutorial: 
   http://www.gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/sec-menus-examples.html

.. and now i want to add a drawing area below the menu, and the source of drawing area is taken from tutorial too:
   http://www.gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/sec-cairo-drawing-lines.html

Now my main.cc file looks like this:
int main(..)
{
  Gtk::main kit(..);
  ExampleWindow win;
  MyDrawingArea area;
  window.add(area);
  window.show();
  Gtk::Main::run(win);
  return 0;
}

So main question is: how to add drawing area and menu that they will be shown together?

Thanks for any suggestion.