Installing American Trucks Simulator mods is pretty easy. To begin, make sure that you've downloaded all the mods that you want to include in the game. Then, head into your computer's MY DOCUMENTS folder, open up AMERICAN TRUCK SIMULATOR, and find the MOD folder. Once you've found this folder, head back to all those downloaded mod installation files. Next, you need to extract these mod installation files (usually, they come in ZIP or RAR form) into the aforementioned MOD folder. To test this out, crack open ATS after you've just installed the mods and open the built-in mod manager. Finally click on the mods that you want to specifically activate, and launch the game to see if it's working as intended.