how to set ring tone downloaded music

music is .m4a and ringtones are .m4r and less than 30 seconds.

Music cannot be used. Google how to truncate and convert music to ringtones.

Buy ringtones from the iTunes Store

• Open the iTunes Store app.
• Tap More.
• Tap Tones.
• Find a ringtone that you want to buy, then tap the price.
• Choose an option to automatically set the ringtone. Or tap Done to decide later.
• You might need to enter your Apple ID password to complete your purchase.

Use tones and ringtones with your iPhone, iPad, or iPod touch - Apple ...