How do I get a ringtone that is in my Itunes Music into my Iphone4?

You must create the ringtone, then you can sync it to your iphone

Google will find several free ways to do this, including using itunes.

Getting ringtones folder to show in iTunes - https://discussions.apple.com/thread/2629494 - iTunes > Preferences. Under the General tab below Show, confirm Ringtones is selected

How to sync ringtones to your iPhone - https://discussions.apple.com/docs/DOC-3792