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 Sound & notification.
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 DONE.
Return to the home screen
Press the home icon to return to the home screen.