The headset mic would probably be the best choice, as it will allow you to hear the audio abovethe rest of the background noise, and is probably a tighter proximity which should keep the rest of the office from mixing with your voice. As for where to plug, on the back of your coomputer, there should be a 1/8" analog jack that has a picture of a mic on it. Plug it in there. As far as USB mics, I have personally never used them as I do alot of recording with analog input.