Your headset, press and hold the main button until it turns blue (or solid colour)
go to settings
accessory settings
and register bluetooth headset
Pass code 0000 (4 Zero's)
to check if it is working, go to voice changer and you should be able to hear yourself talk there
when on COD4, look at the top let, right of the map, if u see a microphone and ))) beside that means your talking, people below your map are people in your team talking