Download the Audacity installer from the Sourceforge website (See Resources) and save it to a directory on the computer's hard drive. Navigate to the directory location where the Audacity installer is saved. Right-click the installer icon and select "Run As" from the shortcut menu. Follow the prompts to enter the credentials of a user account with administrator rights. Follow the remaining prompts to install Audacity onto the computer.
Connect the electronic music instrument or microphone to the computer's "Line In" or "Mic In" port. The process of making this connection varies depending on the type of musical instrument or microphone you're using. Both the "Line In" and "Mic In" ports on the computer are 3.5 mm stereo jacks. Examine the connector(s) with which the instrument or microphone you're using is equipped to determine what type of stereo adapter is needed to plug the device into the computer's "Line In" or "Mic In" port.
Double-click the speaker icon located on the right of the task bar in Windows to open the "Volume Control" utility. Make sure the "Microphone" or "Line In" volume level is raised and not muted.
Plug a pair of headphones into the computer's headphone jack.
Launch Audacity.
Go to the "Edit" menu and select "Preferences." On the "Audio I/O" tab, open the Recording "Device" drop-down menu and select the computer's sound card. Check the box next to "Play other tracks while recording new one." Click "OK."
Open the drop-down menu located just beneath the "Rewind," "Play," "Record," "Stop" and "Fast Forward" buttons at the top of the Audacity window. Select "Line In" or "Microphone" as the sound source.
Click the red, round record button to initiate active recording in Audacity. Begin playing the instrument or singing your vocals. A wave forms on the audio track when sound is being recorded into Audacity. If Audacity is in active record mode and a long, straight blue line forms during the recording, Audacity is not receiving an audio signal. Go over your preparation again to make certain that the computer is properly set up to receive the audio signal. Click the yellow, square button in Audacity to stop the recording.
Click the record button in Audacity again if you'd like to record another musical part along with the music you just recorded. The new part will be recorded to its own individual audio track. You should hear the music you've already recorded, as you play the new part, through your headphones.