Go back to the Finder window and double click the shorter file. Rather disconcertingly it will disappear from the box, but start playing in the background. Don’t worry, it isn’t really gone. Return to iTunes, go to the row of icons in the top left corner and click on the three dots. This brings up more options, one of which is Tones. Click this and you’ll see that the short version of the song is now a ringtone.
Set any song as a ringtone on your iPhone: Sync the ringtone with your iPhone
Connect your iPhone to iTunes and click on the little phone icon just to the right of the three dots. This will bring up the iTunes panel for your phone, from which you want to select Tones in the left hand column. Once inside click Sync Tones>Selected tones>then the track you’ve created. Finally go to the bottom right hand corner and click Apply.
Set any song as a ringtone on your iPhone: Set the new ringtone
All that remains to be done now is to go to Settings on your iPhone, then Sounds, and you’ll find the new ringtone at the top of the list. Tap on it to select it as your general tone.