The thing at the bottom of the screen is not the dashboard. It is the dock. The dashboard is the layer of little programs that fly onscreen when you click the dashboard icon, press F12 on white keyboards, or F4 on aluminum keyboards. I'm not sure you are using the word widgets right, either, but if the widget is a black square with four little white pictures in it, then it is a widget.
To add widgets to the dashboard, just click twice on the black square.