Zoom in tool. Click and drag to create new areal extent for the map.
Note: When you release, the map will zoom to the area approximating you desired area. This depends on the shape of the map window and the rectangle you defined.
Our Preference - Use the PanTool. If you have a mouse with a scrolling wheel, it is much faster to pan the map to center on area of interest and then scroll until you have the extent you want.