Download a program that supports music or audio recording. Serious musicians may want to invest in a full-fledged production program like Pro Tools, Logic or Cubase, but hobbyists can get by with a free program like Audacity, QTractor or Ardour.
Open your software. When opening for the first time, the program may prompt you to create a new project. Otherwise you can create a new project by clicking the "File" menu at the top of your screen and locating the appropriate command. It may read "New Project," "New File" or simply "New," depending on the program.
Locate and open your "Options" or "Preferences." It should appear somewhere among your menu bar options, sometimes under the "Tools," "Help" or "Edit" menu. Under your "Audio Input" options, select your microphone as your primary device. If connecting an external PC microphone, it should appear as the name of the microphone. If using your computer's internal mic, select "Core Audio," "Built-In Audio" or "ASIO" (a built-in sound card driver used by some Windows-based computers and recording programs).
Create a track for recording if necessary. In music terms, a "track" is like a layer. For instance, if you wanted to record a bass, guitar and drum arrangement, you might first record the drums on track one, then follow up with bass on track two and insert a guitar riff on track three, allowing you to record full arrangements one piece at a time. Not all recording programs support multi-tracking, but if yours does, you will find the "New Track" option among your menu bar selections. (See "Tips" for more on tracks.)
Click "Record." With your preferences and your first recording track set up, you can now begin transmitting data through your computer microphone. As the recording begins, start singing or playing your first instrument (or if you're recording a demo, have your full band begin playing). The "Record" button will appear on your main project window, generally along the top or bottom of your screen. Press "Stop" when you finish recording.