Once activated, visit a Scania Truck Dealer or use the "Mod Dealer" tab in the main menu to purchase the customized version.
Most advanced truck mods require the Mighty Griffin Tuning Pack DLC to function correctly, as they often use the slot system provided by that DLC. To help you get the best setup,
Copy the .scs file into your ETS2 mod directory: Documents > Euro Truck Simulator 2 > mod Activate in Mod Manager: Launch ETS2. Open the Mod Manager from the profile selection screen.