Theres a bunch of posts on this...but i will try and give you a quick rundown
First things first:
1) Do you have a micro sd card to store the items on? If not, and if you want to start keeping music on your device, i would def. go out and buy one.
Once you have the sd card installed perform the following:
Go to the Media card menu by selecting
Menu>Options>Advanced Options>Mass Storage>Media Card
Set the following:
Media Card Support:ON
Encryption Mode: None
Mass Storage Mode Support: ON
(2) Plug bb device into the computer, device should mount and display like a little disk. Double click on the icon and you should see several folders (one for music, pictures, video, ringtones.
(3) Locate Your Music (Note can vary depending on your local computers config)
Locate where on your computer itunes is storing your music. On many computers itunes is copying the information directly to the itunes library which is usually located by performing the following:
click on the computer hard drive
click on the "music" icon...(should see an icon for applications, movies, music etc)
Click on the itunes folder
Click on the itunes music folder
You should see your music there
If nothing shows up open itunes and select from the menu:
you should see a box with providing the path to the itunes music folder....locate that on your computer
(4)Adding Music to your Blackberry
What format are your songs in, i would imagine if they are downloaded via limewire they are probably mp3. Not sure all the media types the bb can play but i would think AAC or the protected mp4 which itunes serves up are not one of them. Regardless, you should be able to just simply drag the folder of the artist you want on there or even the individual files. Make sure you place them in the music folder on your blackberry.
(5) Rock out....you should be good to go.