If you click on any button with the right button, a new window will appear explaining what the button does. Clicking on these buttons will change the options available in the buttons window. Click on DRAW . You will draw a chain of carbon atoms. Hold the middle mouse button down and move the mouse in the graphics window to rotate the chain.
Some elements are available in the buttons window.
Choose an element and click on a carbon atom to change the atom type. It is also possible to draw molecules by using templates. A methane molecule should appear. Click on a hydrogen, and the hydrogen turns into a saturated carbon, making an ethane molecule. There are many templates available.