You open the volume control, go to "Options" at the top, select "Properties", and check the box to show the Microphone volume control. Click OK, and there it is, muted by default.
<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>