Once inside the Sound options, choose your Headset under "Output" and your headset microphone through "Input"
You may also need to check your sound settings in the control panel sound options.
Hit the Windows key on your keyboard and type: Sound
You will need to choose the "Change system sounds" which should be the second option from the top when you do the search.
If using Windows 7 or Windows 8, you can right click on the Speaker icon on the bottom right of your screen, and then choose "Playback devices" to go straight to your speaker setup, or "Recording devices" to go to your Mic setup
A windows will popup. Make sure you click on the "Playback" tab on the top left of the window. Once on the "Playback" menu, right click on your headset and then click on "Set as Default Device". You may have to right click again and "Set as Default Communication Device" as well, or if you see a Telephone icon present on the wrong device
Once you set it as the default device, the icon should switch from a telephone icon to a checkmark icon like in the screenshot below.
For the Mic settings, make sure you are on the "Recording" tab and then right click on the microphone you would like to use, preferably from a headset, and then choose "Set as Default Device". You may have to right click again, and "Set as Default Communication Device" as well, or if you see the Telephone icon present on the wrong device.
If you only see one device for either Playback or Recording devices, you may find your issue resolved by right clicking and selecting "Disable", and then right clicking again and selecting "Enable". If the device disappears, right click the empty square and check the box that says "Show Disabled Devices".
Click "Ok" and restart Virbela.