On the left side of the VOSWMM interface, there is a Tool Box which lists all the commands that can be placed on the canvas.
Hover your mouse to the Subcatchment icon in the toolbox. Click the icon and hold the left button of your mouse to drag and drop to your canvas. You will see your mouse cursor change to the Edit mode.
Click on the canvas to draw a polygon. In this example a rectangle
To finish the drawing, mouse Right click will popup Menu, select “Finish Sketch” and the Subcatchment will be added to the canvas.
Use the same way to add the second Subcatchment.