go to menu.... to address book... choose your contact press the menu key again choose edit... when your in the edit screen where you can edit the name and numbers and stuff like that press the menu key again and add ringtone
Set a ringtone for a specific contact
Go to the Address Book.
Click the contact you wish to edit.
Press the Menu key.
Click Edit.
Press the Menu key.
Click Add Custom Phone Tune.
Click the trackwheel to view the list of ringtones and select a ringtone from the list that appears or click "Browse..." to select from the Ringtones folder.
Press the Menu key.
Click Save.