Your time is displayed at the upper left of your screen. Next to the timer is the number of obstacles that are left. Obstacles include walls, rails, tubes, and hurdles, but you only need to take care of the tubes and ramps to finish. The rest of the stuff just gets in the way and knocks you off your skateboard. Grass and turf will slow you down, eventually slowing you to a stop.
Ramps are really easy, just line up with the ramp and get air.
Unfortunately, the 2600 only has one button and that's used to jump and start your skateboard. This delay is really frustrating, and it takes awhile to learn how to skate through pipes without getting your head smashed. Otherwise, the controls are incredibly simple. Move around with the joystick, and use the fire button to jump while on the skateboard. If you get knocked off the skateboard, just press the jump button to get started again.