If this sounds too complex, CSP includes a real-time app. While driving, open the right-side apps panel (mouse to right edge of screen) and find the "License Plate" app. This allows you to type any text in real-time and it will update the plate immediately—no config files required. However, these changes do not save permanently across game restarts unless you use the ext_config method.
Inside your extension/ext_config.ini for the car, or inside the skin folder, add: assetto corsa number plates
[PLATE_0]
TYPE = EU_GERMAN
TEXT = AC · 4711
FRONT_BACKGROUND = white
REAR_BACKGROUND = yellow
TEXTURE_SIZE = 512
CSP will then generate a perfect German plate with the blue EU stripe and the correct font spacing. You can even add holograms and inspection stickers. If this sounds too complex, CSP includes a real-time app