Step 2: From iTunes, right mouse on the created song in AAC format > select “Get Info” > From “Option” tab, you are able to set the begin and the end of the part of the song that you want to make it to be the ringtone.
Step 3: Right mouse on the song that you have just edited, click on“Create AAC Version”. Then make a right click on the short AAC Song which have just been made, choosing “Show in Finder”.
Step 4: You know get back to iTunes to delete the song in iTunes, but be noticed that you click “Keep File”, do not move the file to the Trash.
Step 5: From the Finder Window opened in step 4, change the file ending from .m4a to .m4r. And then click on Use m4r if you see the warning.
Step 6: Drag and drop the above renamed file into iTunes, this should make it shown in your ringtones.