There are instructions about on how to set the camera module to appear as a USB webcam to OpenCV (or is it SimpleCV? It's been a while & I can't remember) but I failed to get it to work.
I settled for taking an image with the camera using raspistill then loading that image into Simple/OpenCV to process it. I got face detection to work like this, although the frame rate is inevitably very low (about one every 3 seconds).
It's not ideal, but it's good enough to get some experience with computer vision while you figure out how to set the camera up properly.