You might need to be a bit more specific. I presume you've a mic with a 3.5mm jack on the end (ie a headset) and you've plugged it into the socket at the front panel/back of your sound card. What version of windows are you using? You might need to double click on the little speaker icon in the bottom right and click on Options, then Properties, then select Recording (make sure the mic box is ticked)and click ok. It should pop up with your input devices, select microphone and it should work. In order to hear yourself though, you'll need to double click the speaker icon again and untick the box under microphone, but have this down low to begin with or you might get a load of feed back if you're close to your speakers