I use Realtek Digital Audio, may be different for you.
General this should woek.
Right click on speaker icon, Open volume mixer. If mic is listed and muted the button under the slide scale should have a red circle with slash. Click to remove the red circle.
Right click speaker icon, open recording devices. Is microphone listed? Has green bar showing if mic is registering sound. Check Properties, General tab. Should show Controller information, Jack information( jack your mic is/should be plugged into) and Device usage, Use this device (enabled)
To test your mic, Start, Accessories, Sound Recorder, Start Recording. A green bar that moves when you talk into the mic should show next to the recording time. Save file as Test. Usually saved to User/Documents folder. Open the file and play back.