Instructions
Launch the game from the PlayStation 3's XMB operating system. Allow it to start and select "My Worlds" from the main menu. This will open the editor.
Press the "Square" button on the controller to open the menu that gives you access to all the building materials.
Create a body for your car out of a light, rigid material such as wood or cardboard. This will form the chassis of your vehicle. Attach a pair of vehicle wheels to the underside. Don't use creature wheels. These will not react properly when you hit the gas. If necessary, simply bolt a round piece of rubber to the base of the body.
Create an ignition switch by dropping a switch on the top of the body. Connect the switch to the wheels using green wires from the "Build" section of the Pop-it menu.
Attach a grabbable object to the top of the chassis and glue it in position. This will allow you to cling on while the car is in motion. Sponge is a good choice.