1. Connect the USB cable to the monitors USB type B port on the back of the monitor. Then attach the other end of the cable to an available USB port on the computer. Allow 10-15 seconds for the computer to recognize the external webcam.
Note: This method will also work to connect other USB webcams to the computer.
2. Select the "Photo Booth" program from Applications folder or from the dock at the bottom of your screen. This is an Apple supplied program that uses the webcam to show you live video of yourself.
3. On the Photo Booth menu bar there is a Camera drop down menu. Click on it and select the external USB webcam from the list once it has been detected and installed. The computer will switch from the default iSight webcam to the external webcam.
Note: Mac programs are all in sync with one another, these settings will be used for all other installed programs on the computer.
Additional information can be found directly from the Apple site in the link below.