– download the ringtone in your computer

– open iTunes

–  connect your iPhone with the computer and select the icon of the device on the left sidebar

– click on the bell icon

– drag in the ringtone

– update your smartphone

– select “settings” on your iPhone > Sound > Ringtones and select “Ringtone #rossodesiderio” to set it as the default ringtone of the phone

–  if you own a Mac, download this app on your computer

– download the ringtone on your computer

– connect your smartphone to the computer 

– drag the ringtone in the “Ringtones” folder

– select your smartphone’s settings > Sound > Ringtone and select “Ringtone #rossodesiderio” to set it as the default ringtone

If you own a pc you’ll only need to connect the smartphone with the computer, open “Explorer” in Windows and select “Computer” or “This PC” on the left sidebar.
Double click on the icon of your smartphone and then drag the file in the specific folder.

NB: if the sign “The folder is empty” appears, it means that the USB connection is not set up for file transfer.
To solve the problem, just go on the Android device, go to the notifications area, select the notification about the USB connection and choose the “File transfer” (MTP) option from the menu.