First you have to download the Estering, Germany add-on. Once you have go to Freeplay > Custom > Create Championship. Select Add Event and scroll over to find Estering and select it. Set the Format to Single Race, Vehicle Class to RX Supercars, and whatever weather and laps you want. From the Championship Configuration screen you can also use
for Customise Championship and set the AI difficulty to Very Easy. When you're ready, start the Championship. For your car you need the Ford Fiesta Rallycross MK8 and before you confirm it, press
to select a livery and choose livery 2/7. Then just win the race and the achievement is yours.