Here is the instruction as below:
Step 1: Open iTunes.
Step 2: Find the song that you want to make into a ringtone.
Step 3: Listen to the song and find the part of it you want to use. The chorus may be a
good place to start.
Step 4: Write down the start and stop times of the clip.
Step 5: Right-click the song and select "Get Info."
Step 6: Click the "Options" tab.
Step 7: Type in the start time of your ringtone in the text box next to "Start Time" in
the minutes:seconds (i.e., 2:01) format.
the minutes:seconds (i.e., 2:01) format.
Step 8: Type in the end time of your ringtone in the text box next to "Stop Time."
Make sure the ringtone is no more than 40 seconds long.
Step 9: Click "OK."
Step 10: Right-click your song again and select "Convert Selection to AAC." Wait for
iTunes to convert your song. It will create a duplicate version.
Step 11: Right-click the ringtone and select "Show in Windows Explorer." It will show
you the place of file. It will have an extension of m4a.
Step 12: Change the m4a extension of your ringtone to m4r. Right-click and select "Get Info" on a Mac or "Rename" on a Windows PC.
Step 13: Click "Yes", when the system warns you that the file may become unusable.
Step 14: Double-click the ringtone file. ITunes will automatically add it to your ringtones folder in your iTunes Music Library.
Step 15: Connect your iPhone and sync your ringtones or Simply drag this file to the iPhone icon in iTunes.
That’s it. Your newly created ringtone should now be visible in the iPhone and you can start using it rightaway.
