Step 1: Stuff you need
A male headphone jack
A breadboard or experimental circuit board (optional)
Step 2: Wire it up
Step 3: Connect an antenna to it
Step 4: Tune your radio
It may take a little time to find your station but it should work.
The louder you turn your music up, the louder it will be on your radio.
-I also found a better version of this. It uses a modulator. This improves the system a ton. Check out the second picture to see this with the modulator.