Connect your iPhone to the computer.
Activate the sidebar if it is hidden. Because there you can now see your iPhone. Extended options, if not already implemented. Sync audio with iPhone
There you will see the subsection "Sounds". Click it. Now drag the previously created m4r file to the list in the iTunes window. Once you do, your iPhone will sync the ringtone to the default settings.
Now open the "Settings" app on your iPhone and select "Sounds & amp; Haptics". You can find your newly added tone in the "Ringtone" list.