When you start Sailaway and log in with your email address and password, you will find yourself on board Tessie with the mainsail and genoa up.
To steer, press the Z or X key.
To adjust a trim line, press the Q or E key to select the line and then press R to release or F to pull.
Move the mouse pointer to the right bottom corner of the screen and click the ? that will appear to pull up a list of more key commands.
Other controls can be found in the popup menu that will come up when you click the boat.
Check out the basic instructions video
here
General documentation and a User Guide can be found
here
Specific documentation for Tessie can be found
here