How do you download ringtones to the Motorola Rokr?

I have a Motorola Rokr that I am trying to download ringtones from phonezoo to my phone. I have the audio but I can't get it to go to the ringtone.|||get ringtones online and download directly to your phone through WAP or SMS. You can also choose to download tones to your pc and then transfer them via usb data cables or blue tooth.