To run the game, you need to own a legal copy of the game and activated it on your Steam profile; You can only have one TruckersMP account per one Steam account (so avoid getting banned); You can run the game with your Steam account in Offline mode (however, you won't be able to see your friends, marked in green, in the game);
Multiplayer isn't a function of the game. It's a fan-made mod, that right now isn't compatible with the current version. So if you do want to play multiplayer, you have to learn how to downgrade your version, and then join the server If you want to play Euro Truck simulator 2 as intended you will need to fill your tank from time to time. Locate nearest gas station, stop your truck right at the spot of canister icon, turn off engine by [E] then hold [Enter] until your tank is full or you reached the amount you wanted to fill. Dcl2u.