Audacity is a free audio editor that works on Windows, Mac OSX, and Linux / Unix computers. One of the coolest things about Audacity, besides its cross platform compatibility, is that all of Audacity's program files fit into one folder when it is installed. I keep a copy of this folder on my USB flash drive, and whenever I need to make some quick audio edits at a friend's house, I just plug my USB flash stick into my friend's system, and Audacity runs perfectly without having to install anything on his computer.
If you don't have Audacity, download the installer from http://audacity.sourceforge.net Once the installer is downloaded, click on it and follow the routine instructions. When it is finished, open the program.
You'll want to set up a few things before your first recording. First, go to Edit in the tool bar at the top of the screen, and choose Preferences. When the Preferences control panel opens, go to the Audio I/O tab. The Audio I/O dialog selects the input at which your microphone signal will be picked up, and which jack the final output of your audio will be routed to, on its way to your speakers or headphones.
If you only have the built-in sound card that came with your computer, you probably only have one input and output, so chances are that your settings are already selected correctly for you. However, if you have an audio interface with multiple inputs or outputs, select the input to which your microphone is connected, and make sure your speakers or headphones are hooked up to the selected output.
If you wish to monitor the sound from the microphone while you record, check the check box at the bottom of the dialog labeled “Software Playthough.” Next, switch to the Quality tab.