There should be an icon for it on the Windows desktop. Double-click that and a window should open showing the view of what the camera see (usually it's your face!)., just like the screen on a digital pocket camera.
It depends on the webcam software, but on mine you then click the camera icon at the bottom of that window it saves that image in "My Pictures" as a "JPG" file.
There is not an icon on desktop or in start menu