Find "Phone ringtone"
Slide two fingers down the display starting from the top edge of your phone.
Press the settings icon.
Press the settings icon.
Press Audio profiles.
Press the settings icon next to "General".
Press Phone ringtone.
Select your ring tone
Press the different ring tones to listen to them.
Once you've found a ring tone you like, press OK.
Return to the home screen
Press the home icon to return to the home screen.