You are in a race so you should come up first. There are only three of you in the race and the second and third places are no good. To accelerate, pres and hold the up button, while the left and right arrow key will help you to determine which way you want to go.
The game control seems a little difficult so you may want to do some practice first before the race. To do that, choose the single mode and practice to your heart’s content. Once, that, you have mastered the control then you can switch to the challenge mode.