You need to go into music and find it there. Click and hold the specific ringtone for a few seconds and a menu should pop up. Delete will be an option. I you want to remove it as a ringtone but leave it available as music, use the usb cable that was provided with the phone. Hook up to a laptop or whatever you have. Your phone will open up like a regular drive (A:, C:, D:, E:, etc) and you can delete it there also or move stuff around.
You cannot remove any stock ringtones (ones that came with the phone)
Hope this helps.

How do i delete ringtones of of my samsung galaxy centura