Newly bought Headset with Mic is not working

Hi guys,
I have brand new headset with mic, have a black and red port. On June 30 and July 3, I have schedule for an online interview. I need to ready my headset on that days. But the problem is when I tried to call my friend on YM, she doesn't hear me. But me, I can hear her voice. I don't know to fix it, I don't have any idea. Actually this is my first time of having a headset with mic. Before I have headset but without mic. Guys please help me, tell me the settings for this problem. Thanks.
