To select by windowing you draw a window around one or more shapes to select them. To draw a window around a shape first position your mouse pointer above and to the left of the shape(s) that you want to window. Then depress and hold down the left button on your mouse. While keeping the left button depressed drag your mouse to a position below and to the right of the shape(s) that you want to select. Finally release the left mouse button. Note the following about window selection:
As you drag your mouse a "rubberband window" appears. The rubberband window is a dashed rectangle that changes shape as you drag the mouse. One corner of the rubberband window is at the point where you first depressed the left mouse button. The diagonally opposite corner of the rubberband window is at the current mouse pointer position. Any shape that is completely inside the rubberband window when you release the left mouse button is selected.
You do not necessarily have to start the window above and to the left of the shape(s) you are selecting. You could alternatively start the window above and to the right, below and to the left or below and to the right of the shapes(s) you want to select. In all cases you would then drag your mouse diagonally across the shapes(s) you want to select.
An entire shape must lie within the rubberband window for the shape to be selected.