Download and install Audacity (see Resources).
Connect your microphone. If your computer has an internal microphone, you won't need to connect an external microphone. If your computer does not have an internal microphone, you have a few options. If you have a USB microphone, connect it to a USB port on your computer. If you have a regular microphone (such as a Shure SM57), connect a 1/4 mono to 1/8 stereo adapter to it and plug it into your computer's microphone port.
Open Audacity.
Click on "Edit," and then scroll down and click on "Preferences."
Click on the "Device" drop-down menu under the "Recording" heading and select your microphone. Click the "OK" button.
Press the "Record" button (the red circle) and speak/sing/play guitar/etc. into the microphone.
Press the "Stop" button (the yellow square) to stop recording.
Click on "File," and scroll down and click on "Save Project As." Click on the "OK" button in the "Warning" window.
Enter the name of your project into the empty "File Name" field and click on the "Save" button to save your project and audio file.