To start the game, you have to press the "Play" button. You can also press the "How to Play" button which directs you to this website. The "Quit" button will close the game.
After pressing the "Play" button, you can choose the Gamemode. The button "Back" brings you back to the Main Menu. After selecting the Gamemode, the race will start. If you down know how to race, you will find help here.