Select a button with geometry to start drawing it with the left mouse button.
For the circle select center and draw the radius
Press SHIFT key to freehand drawing.
Select trash button and then a geometry to delete it.
Add new vertices clicking along a line.
Vertices can be removed by holding down the ALT key.
To reset changes click the button with the arrow.
To cancel changes click the button with the X.
To confirm changes click the button with the check mark.