How do you start a company on 18 wheels of steel haulin

You don't really start a company in the traditional sense. What you can do is hire a driver, after three deliveries and then purchase an additional truck and a trailer. You then go to the objectives screen (shortcut N) and click manage contracts. You will now be able to contract your driver to one of the companies that you have delivered for. It should be noted also that you find drivers at the hotels throughout the game for hire.