Instructions
Place the MP3s you want to use on your desktop for easy access during the MP3 placement process.
Click on the start menu and navigate to the "My Documents" folder. Find the "EA Games" folder and click on it to open it up. Open the "The Sims 2" folder and then navigate to the "Music" sub folder. Select the radio station folder in which you want to place your MP3s.
Select your MP3s and drag them to the radio station folder. Wait for them to copy and then close the folder.
Start "The Sims 2" and turn on your radio. Turn to the station to which you placed your MP3s to check whether or not your MP3s moved. Keep listening until you hear your songs.