On the Set Area Boundaries window you can change the geographical extent ("area boundaries") of your study area. The current boundaries are shown as a green rectangle; click and drag on the large map to specify new boundaries. If your area is small in relation to the world map, you may need to zoom in so that you can choose your area accurately. Hold down the control key while clicking and dragging on either the large map or the inset map to select the rough area to zoom into; hold down the shift key while clicking and dragging to pan the map. Rotating the mouse wheel will also zoom in or out.
Menu Option: Schematic: Set Area Boundaries