*UPDATED*
Fairly self-explanatory, win the championship with the C.O.T. car.
This can be simmed. I would suggest though if you go this route that you pick a fairly good driver. and set your opponents to the lowest difficulty. If you are close points wise at the end of the season, it might be a good idea to race to ensure yourself the victory and the points championship.
Good luck!
*Update* As ARM BM mentioned, you can narrow the field down to 11 drivers and still obtain this achievement. I thought I had read somewhere that you had to have a full field of cars in order to get the achievement and I did so when I got it, but, it appears that information is incorrect! Thank you for the info ARM BM!