(1) The microphone plugs into a hole in a sound card (at rear of computer) along side of other holes, one of which the speakers plug into. 
(2) Set the mic switch to the on position if it has a switch.
(3) Select  Programs, Accessories, Multimedia, Volume Control*, Microphone, and select microphone by clicking in the select box.
(4) Select Programs, Accessories, Multimedia, Sound Recorder, click on record button to record.  As the mic is spoken into, a green line should indicate the sound being recorded.
(5) Save recorded sound as a Wav file to a sound folder you have created or save to the desktop so you can find the file easily.  (Use the Save As option so you can choose a name and location for the file)
(6) The Wav file you create can be attached to an email or used in place of any of the sound files used in windows.  (See control panel sounds icon)

* If you don't see microphone listed when you click on volume control, then select options, properties, and place a check mark by microphone, then click OK.  You should then see microphone listed along with other items that were selected.

Advanced users can turn off microphone setting and select Inline Record and record from a CD to a sound file, customize the wav file to last only about 10 to 20 seconds and use it as a Windows start up or other sound uses.  Windows only uses Wav files so convert any other types of files to Wav files.