The following steps apply when Messaging is set as the default app.
From a Home screen, swipe up to access all apps.
From the Inbox, touch and hold the message containing the ringtone.
Tap the Save icon .
By default, the sound file is saved to: Internal Storage/Download.
To view the sound file as a ringtone option, it can be moved to: Internal Storage/Ringtones via File Manager.
To set the ringtone, refer to Set Ringtones.