They're two ways to get this. First you must find an event that has two races. You must place second place in both races and as long as the driver from the first race that got first does not get first in the second race it will unlock. The second way of doing it is driving with a teammate. Simply trail behind them guarding them from any other driver approaching him. He must get first place in every race that's in the event. Any teammate will do. Your winning position does not matter as long as he is in first place.