1.  Connect the LifeChat USB headphones to the USB Port on the MacBook Air.

2.  Go to Apple > System Preferences > Sound

3. Select the Output Tab and select the Microsoft LifeChat headphone for Sound Output like the picture below:

4.  Select the Input Tab and select the Microsoft LifeChat headphone for Microphone Input like the picture below:

5.  You can check the microphone input level by speaking into the microphone and checking the Input level meter.  If you need to adjust the microphone Input volume, use the Input Volume slider.  A normal volume will typically peak in the upper third of the Input level meter.  You will get the best results if it doesn't continually peak at the top of the Input level meter.

6.  Please be aware that there are additional headset volume controls on the Microsoft LifeChat headphones as well as a microphone mute button that lights red when it is on.