Open the MyJio app
Sign in with your Jio number
Tap the JioTunes or Caller Tune option
Search for a song or browse the available list
Select the song you want
Tap Set as JioTune
Confirm the activation
Wait for the confirmation SMS
Use the JioSaavn app if JioTunes is linked there
Choose a song and activate it from the app
Check that your Jio plan supports free JioTunes
Deactivate any existing caller tune if needed
Recheck activation from the MyJio app if it does not set immediately