You probably need to win some "outrun" races. (I didn't know this at first either). The orange triangles on the map are other racers. You need to get close to one and you will see an icon pop up on the top left corner (there will also be a sound like an incoming instant message). You must stay close to the other guy to keep the icon visible. When you are ready press the enter key (?) and you are off. You need to get a certain distance in front of the other guy to win and he will try to outrun you as well. You will need to win a certain number of the outrun races to advance to each new level.