You will be required to either win two Drivers' World Championships in career mode or online Co-op mode, each with a different team.Online Co-op is by far the easier choice, as you will have a friend to back you up and help you out by crashing off the competition.Once you are done with your first season and you win the WDC, start another one and select a different team.
If you consider doing this in career mode, be advised that unless you are a skilled/seasoned driver you will need to wait to get promoted to a better team than the one you are starting out with. After winning your first WDC, you will need to switch teams to win it a second time.
Don't worry though, after winning the WDC you will have enough offers on your table.In any case, make sure to set the A.I. difficulty to Amateur to help you get this achievement faster.