You need two Things first:
1.You need to do is install the "Blackberry Desktop Manager" on your computer. Its the CD that came in the box with the BB.
2. A Micro SD card (sizes go from 1G and up, Price from 30 and up)
After you install the "Blackberry Desktop Manager" you will connect it to your computer via the USB cable. (Oh but before you do you need to do some setting changes on your phone. Go to Settings > Advance Options > Media Card > Mass Storage Mode Support > ON) Your device will also ask you if you want to turn it on when it sinc's up to the Desktop manager. Click YES
Then click on the Media Manager on the Blackberry Desktop Manager. This will open up The Roxio program. There Willl be a window with Two boxes. The top one will have you Computer Media Folders and the bottom will have your BB device with 4 Folders Music, Pictures, Ringtones, Video.
So just click on the Folder where your Media is at on your computer and click on the Copy Down to one of the Media folders on your device.
If you dont have that Desktop manager version with the Roxio Media manager i strongly suggest you to download it from Your wireles providers web page or from Blackberry.com
This will allow you to make your own rintones.
All you need to do is
Start > Media Manager 9 > Audio > Easy Audio Capture.
And from there you need to make some setting. .
Input > Stereo Mix
Capture Settings > iPod ACC good quality
Recording Level > Auto
File name prefix > Song title
So you can record a full song or record a 30 second bit of your favorite song and latter upload it to your media card and set it as your ringtone. And its free.