Instructions
Insert your GTA: San Andreas game disk into your game console and wait for the flash screen to give way to the main menu screen.
Get into a car and open your map screen by pressing the "Start" button on your controller.
Locate the red wrench icon on the city map screen. This marks the location of a modification garage. All three of the city maps in GTA: San Andreas have at least one garage.
Drive your car to the location of the garage and pull up right in front of it. A garage door will lift open. Drive your car into the garage.
Wait a few seconds for the modification to take place. When it's finished, the garage door will lift up again, and your car will be completely modified--with a new paint job and accessories.