Click on the plus sign next to brick.
Go to 
.
Drag it over to the top view window. This is the base of your car.
The first thing we will add is wheels. In your parts
area that looks like this click on Other Parts.
Go down to W and click on the plus sign. We will now look for tires and wheels.
You will want to split your parts window screen. It
should like this.
If you need to
adjust the window click on the line in between the 2 windows and drag it up
or down.
In the bottom window you will see the different tires.
Pick a tire that will fit your car well. I picked this
tire. 
After you do the tires be creative and finish off the rest.
Here is a picture of the beginning of mine.
