|Your headset may or may not be detected by your version of OS X. Use the same instructions that were given to the previous poster to get to the Input pane in Sound within System Preferences. Look for "External Device", "Line-in" or a generic name if your headset's make and model is not detected.|
Also, to decrease static, lower the volume in the Sound preference pane, turn off cellular devices near the computer, and if you happen to have any fans or sound equipment near the mic, turn these off.
Let me know what else you need help with. :)