Nokia Lumia 900

Find "ringtones + sounds"

Press arrow right to access the main menu.

Find "ringtones + sounds"

Press Settings.

Find "ringtones + sounds"

Press ringtones + sounds.

Select ring tone

Press the field below Ringtone.

Select ring tone

Press the playback icon next to the different ring tones to hear them.

Select ring tone

Once you've found a ring tone you like, press the required ring tone.

Exit

Press the Home key to return to standby mode.