Question: how to add ringtone to iphone x from itunes?
Answer: Connect your device to your computer.
Open iTunes. ... 
On your computer, find the ringtone or tone that you want to add to your device. ... 
Select the tone that you want to add to your device and copy it. ... 
Return to iTunes and go to the Library tab of Music.
Click on your device in the left sidebar, then click Tones.