You can open the widget area just by clicking the arrow right from its title. Assign widgets to the area just by dragging them into open widget area below its description text. When no widget is assigned to the widget area, it will not be displayed.
Bistrap creates 8 predefined widget areas:
This area is displayed as default sidebar.
This area is displayed below primary sidebar.
Footer Sidebars (1-6)
Website footer sidebars lets you create amazing website footers.