Is there an app which will make or import ringtones?

Hi all.
I am wondering if there is an app which will let me create ringtones directly, such as playing a song. I would also like to take something I have previously recorded, such as my cat demanding his treats and turn that into a ringtone. Is this possible? The only iOS device I have is an iPhone 6. I do have a computer running Windows 7. I once heard that Garage Band for the iPhone can make ringtones, but I figured the best place to ask was here.
Thanks in advance for the help.