toolbox

The button that corresponds to the selected tool should be depressed in the toolbox. What if the toolbox is closed? Simply move the pointer over the stage to see which icon appears. Most of the pointer icons for the drawing tools correspond to the icons in the toolbox.
If the toolbox does not appear on your screen, you can open it by choosing Window > Tools. You will see a check next to the toolbox menu item if it's open.
Some of the drawing tools create only strokes. You can use the pencil tool to draw freehand lines and shapes—it's a lot like drawing with a real pencil. The pen tool is useful for drawing precise paths as straight or curved lines, and the line tool is great for drawing basic shapes that are composed of straight lines.