Controls: Use left-right arrow keys to steer, up-down to accelerate, decelerate and space to brake. R reset the car.
Start a new multiplayer game: Click on the Multiplayer option, followed by clicking on the Start a New Game button. You can then enter a Name for your Game Session and click on Start button, the game will automatically start once another player joins. If you don't want to wait for another player then click on the Start button.
To Join another Players game, click on the Join an Existing Game button and then click on the Connect button, next to the game you wish to join. The game will start once you've joined.