This achievement you earn through the RallyCross portion of the career. From the main menu, choose Events and head into Career. Choose the RallyCross discipline. The first event you can choose is the National Race A which is the RX Super 1600s Cup. There will be 6 races total you will need to win; 2 races at Montalegre - Portugal, 2 at Holjes - Sweden and 2 at Lydden Hill - England. I'm actually not sure if you need to win all races, I did though to win the Championship. To make things easier just change the AI difficulty to Competent.