I am sorry if no one answered your post until now.
Here is how to proceed:
1. On the Home screen, click the Sounds icon.
2. Click Set Contact Alerts.
3. Click Add Contact Alert.
4. Press the Menu key.
5. Click Add Name.
6. Click a contact.
7. To add additional contacts, repeat steps 3 to 5.
8. Click the application or item that you want to change.
9. Change the ring tone or alert information.
10. Press the Menu key.
11. Click Save.
Please note that you can find this information in your user guide. Here's a link to it : User Guide.
I hope this helps!