Ok, here is what you need to do. The speed control, the little computer chip looking thing that has a metal piece that will slide across it needs to be in the middle when you turn on your car. Here is how you get it set up to run properly. Take off the top to the car and unplug the motor. Now you need to turn on your car. The little computer chip looking thing with the metal thing that can slide across it needs to be lined up right down the center for neutral. When it slides off to the left or right it is in reverse or neutral. Now, your radio has differant settings. One of these is going to allow you to control where the servo centers. Make sure this is adjusted so that the servo is currently centered. Now remove the servo horn that is attached to the speed control. Now put the servo horn back on to the servo but this time make sure the metal sliding piece on the speed control is lined up down the middle, it more then likely will not be perfectly alined, but make sure it is close. Now you need to use the same setting that centers the servo to make sure that the throtle is lined up dead down the center. Plug your engine back in and go drive. If the car goes in reverse when you want forward then check your motor conections first, make sure that you plugged the right wires up. Then your radio has another setting. This setting will allow you to reverse the direction the servos spin. This is just a little switch. To get the steering lined up, if it is not centered then do the same thing you did with the throtle. Before you take stuff apart though check and see if you can fix the problem by just adjusting how the servo centers with the radio. If the servo is going to limit the cars performance and not swing far enough then you will need to refit the servo horn like I said.
Good luck and be sure to have fun.