Ok the mic confused the heck out of me for days. This is how it works, I think...
Plug your stuff in, make sure your settings in COD allow voice chat. Should be on by default. There are other settings but I think they are pretty balanced by default so you should be able to hear everything.
Important thing, make sure the sound on the actual Gamepad is turned up. Other wise you will cut out your own voice not matter what the actual head set settings are.
If you see your name pop up on the top of the screen while you talk, during battle they should be able to hear you.
I kept losing out on horrible conversations because the gamepad was turned down.