This is very basic, but I need to know how to transfer a song from my iTunes into Limewire. Thanks!

There are two ways.

1) Make sure your Limewire Prefs>>Player has Limewire's internal player deselected. Then make sure you have iTunes set as your default mp3 player. Then you can simply double click mp3 files in your Limewire Library or from the search window after the download is complete and it will automagically play the file and add it to the iTunes Library.

2) Open your Shared Folder and drop and drag the desired mp3 files to your open iTunes application.

I think you're asking how to share your itunes music with other LimeWire users? You can add folders to be shared by choosing "Preferences..." from the LimeWire pull down menu at the top of your screen, then choose "Sharing". From the "Sharing" pane, you can click on "Add" to choose folders for sharing. In addition to the default folder, I've added the folder that contains the mp3's I've ripped from CD's. (Users/Your User Name/Documents/Itunes/Itunes Music) and the folder where I keep music that friends e-mail to me. (/Users/Your User Name/Music). Every folder below these folders will also be shared.