Create or choose an audio file in M4R format
Keep the ringtone under 30 seconds
On Mac, open Music or Finder and select the song
On Windows, use iTunes to import the audio file
Convert the song to AAC if needed
Change the file extension from .m4a to .m4r
Connect your iPhone to your computer
Open Finder on Mac or iTunes on Windows
Drag the .m4r file to your iPhone’s Tones section
Sync your iPhone
On iPhone, go to Settings
Tap Sounds & Haptics
Tap Ringtone
Select the new ringtone
Use GarageBand on iPhone to create a ringtone directly
Export the GarageBand project as a ringtone
Set the exported sound as your ringtone in Settings