Drawing
The toolbar has bond, arrow, bracket, text ring, and symbol tools for drawing. The use of these tools is summarized in the Toolbar reference.
Tutorial exercise: Cinnamaldehyde
Draw the benzene ring first. Click and hold the 
Ring tool. Go into the Rings submenu. Select benzene. Left-click in the drawing area to draw a benzene ring.
Now draw the side chain. Click on the 
Bond tool. Move the mouse over an atom in the benzene ring and left-click to start drawing. Drag the bond into place and release the button. Repeat this process until you've drawn all the single bonds necessary for cinnamaldehyde.
We need to insert two double bonds. You can do this two ways, so we'll do each double bond differently. Use the Bond toll to draw over the existing bond to form the alkene double bond. Then choose the 
Select tool and right-click on the aldehyde C=O bond. Choose double bond in the dialog and press OK. Note you can also change other properties of the bond this way.
Now we need to label the aldehyde O and H so it's clear that this is cinnamaldehyde. Choose the 
Text tool and click on the end of the double bond -- make sure the end point is highlighted. Type "O" and press return. Then click where the H should be and type "H" and press return.
And there you have it -- cinnamaldehyde!