In the bottom right corner of your screen, you will notice the volume icon in the system tray.
Right-Click on the volume icon and click Open Sound Settings.
In the Sounds Settings window, look for Input and Choose your input device and then click the blue Device properties link (circled in red) in the screenshot below..
This will pull up the Microphone Properties window. Click the Levels Tab and you will then be able to adjust your microphone volume settings.
The volume level does not have to be at 100%, but should be high enough that the computer can detect audio.
Please make sure that your microphone is not muted. If you see the icon below, click the speaker icon to un-mute.
Once you determine the best settings for you and your system, click OK to save the settings and then close all settings windows upon completion of adjusting your microphone volume settings.