Get a recording device. This can be a standalone digital or analog recorder, a computer program or simply an old tape deck you may have laying around your parents' (or grandparents') garage.
Get a microphone. Alternatively, you can plug many electric instruments straight into your recording device, or you can grab a pair of headphones and plug them into the input jack on your recording device.
Obtain the wires you need to record your instruments. This varies depending on what microphones you're using, what recording devices you're using and, most importantly, what types of musical instruments you're using.
Press record and play your music into your recording device. Once you're finished recording your music, play it back and hear what it sounds like. Repeat this step until you are happy with your recording.
Share your music with the world. If your music is already on your computer, mix it down into an .MP3, .WAV or other file that you can easily share with your friends. If you have your music recorded on an analog tape, you can either copy it to another tape or use your tape player's output jack to run it into your computer using a 1/8-inch plug, and record it using some recording software.