On the latest versions of Android, to add a downloaded song to your list of ringtones, open Sound → Ringtone → Media Storage, scroll down to the bottom and click Add Ringtone, which will open the built-in file manager. Using Explorer, navigate to the folder with the downloaded audio file and click on it. And you can download ringtones on the All Ringtones website. I downloaded peacemaker ringtone https://all-ringtones.com/731-peacemaker.html there, quickly and easily