To use a received sound file as a ringtone, refer to Save a Ringtone for assistance.
From a Home screen, tap Apps (located at the bottom).
Tap Settings. If unavailable, tap the Dropdown menu (located in the upper left) then tap Alphabetical. If still unavailable, refer to Manage App Icons.
From the DEVICE section, tap Sound & notification.
From the INCOMING CALLS section, tap Ringtone. The 'Sound profile' (located in the GENERAL section of the 'Sound' menu) must be set to 'Normal' in order to modify ringtones. Tap Sound profile to change its current setting if needed.