If your a newbie to DSLR's then I recommend you stick to your sports setting (the dial on the top of the camera, probably a strange shaped stick man running)
Also read the manual, when I first got my DSLR I had no clue what to do but a 20 minute read of the manual taught me all the technical stuff like changing lenses, what aperture is, how to focus properly.
Once you've learnt the basics just do a google search on sports photography tips, you'll get lots of pages teaching you how to do things like pre-focus (where you focus on a bit of the track manually, then when the car goes past it you take the shot - this way you don't need to mess around with the relatively slow focus of the lenses you have. (When I say slow, this is compared to the Canon Professional USM series - which are pretty close to instant in good lighting))
Hope that helps.