Hey
Welcome to the forum!

Right click the sound icon in the notification area of your taskbar and click recording devices.
Plug the headset in and tap or blow the mic, whichever device shows some activity, right click and click set as default device.
This should get you going.
Sometimes these headsets you get from the £1 store don't work as good as they should, but ya'no, only a £1 right?
Any problems, just post back!
Daniel =)