to get a ringtone out of your personal CD collection, you need to rip the CD to your computer, use Audacity or some software to edit it to about a 30 sec ringtone. Then transfer that ringtone to your Media Card.
You can try to fomat the SD card on your BB or the PC, if you have an adaptor. when you get it formatted, on the BB, enable mass storage on your Media Card (Options > Advanced > Media Card). How do I get ringtones on my BlackBerry? - BlackBerryFAQ