To draw a freeform shape:
Select the Freeform Scribble Tool.
Click and drag to position the first node and start drawing a line.
If you make a mistake, press the Escape key to delete the whole line and start drawing it again.
Release the mouse to end drawing at any time.
To draw a closed shape, end drawing sufficiently near to the first node to display the mouse text "Release Mouse to Close". This will join the end of your line to the first node.
You can adjust your shape in various ways using the Pointer, Reshaping and Rotation Tools.