When you launch the game on the PC (Steam install) a configuration window will open, letting you control the video options, i.e. graphics detail settings (Resolution, AA, AF, Texture Quality, etc.).
Tip: There are a few races that are quite taxing on the PC hardware, you might want to turn down AA (Anti Aliasing) for those "laggy" races to win them more easily.
Regular Setup Edit
This can be done in the menu just before the game starts, including audio volume, and a few other things.