1. You should own one of the games below:
- Euro Truck Simulator 2: http://store.steampowered.com/app/227300/
- American Truck Simulator: http://store.steampowered.com/app/270880/
2. Sign up at https://www.worldoftrucks.com/en/join.php
3. After signing up, go to https://worldoftrucks.com/en/events.php
4. Click on "Metallic Paint Jobs - Free paint jobs as a thank you!" and activate your key.
5. You could also win another DLC if you complete a quest:
"Help Santa and Save Christmas! Truckers round the globe unite to help deliver Christmas gifts while Santa is busy chasing evil spirits in the form of Dragons.
Goal: Deliver gifts to at least 10 DIFFERENT cities across European and American continents.
Reward: Event-exclusive Dragon Truck Design DLC and a special World of Trucks achievement.
You will not be able to buy this DLC, it has to be earned!"