Find "Phone ringtone"
Press Settings.
Press General.
Press Phone ringtone.
Select ring tone
If you want to use one of your phone's default ring tones:
Press Ringtone.
Press Ringtone.
If you want to use one of your own ring tones:
Press Music.
Press Music.
Press the different ring tones to listen to them.
Once you've found a ring tone you like, press Apply.
Return to the home screen
Press the Home key to return to the home screen.