Slide your finger down the display starting from the top edge of your mobile phone.
Tap the settings icon.

Tap Sounds and notifications.

Tap Ringtones and sounds.

Tap Ringtone.

To use one your mobile phone's default ringtones:
Tap the different ring tones to listen to them.

Once you've found a ringtone you like, tap the Return key.

To use one of your own ringtones:
Tap Add ringtone.

Tap the different ring tones to listen to them.

Once you've found a ringtone you like, tap DONE.

Tap the Home key to return to the home screen.