Enabling microphone is Alsa

To get the microphone working, type into a console....

alsamixer

Make sure under "Digital" the "i2s in" option has been chosen ("is2 mixer" is also a possible choice). Tab through "View" and make sure that all appropriate "mute" switches are turned off and all sliders are up (though not too far up as this can cause feedback).

Another alternative is to open up the "Volume Control" and adjust the controls there. If desired, turn off the microphone when not in use by using the microphone "Mute" switch.