The point of this tutorial is to teach you how to create a quick sketch that captures the essence of the car and its proportions, not a photo realistic illustration of the car. I use Photoshop and a graphic tablet, but you should have no problems drawing the car's basic shape with a regular pencil and a sheet of paper.
Take a look at how the relevant points that dictate the car's proportions (where the windshield starts, where the rear of the car starts and ends, etc) are placed relative to the wheels drawn at the beginning. It's all about joining those points correctly, with either straight, concave or convex lines. _