Oh, so you do
already have a specific webcam, and aren't just asking about webcams in general? That's helpful to know
Again, you need to provide much more accurate input if you want help. What exact commands did you try typing? What error messages did you get? As I often say, I'm afraid we're not mind readers
If you're only interested in recording video, you'll probably get much better results (and much more help) if you use the official RaspiCam http://www.raspberrypi.org/archives/3890
USB webcams are quite variable, so what works for one model may not work for a different model. And on the RaspberryPi they tend to be quite slow.