Sounds great except, my rugby does not have a USB port on the bottom of the phone, just a charging port on the right side.
Download ringtones in your PC. To transfer them to your phone, follow these steps:
Touch "Applications | Settings | Wireless and Network | USB Utilities | Connect Storage to PC" on your Samsung Rugby Smart.
Plug the larger end of the USB cable into your computer's USB port and connect the smaller end to your Rugby's bottom USB port.
Click "Open Device to View Files" from the AutoPlay menu.
Double-click "Phone" to access your Rugby's internal storage. Alternatively, if you have a microSD card installed, double-click the SD card.
Drag and drop files between the phone's storage locations and your computer to transfer them. If you want to transfer photos from the phone, find them by clicking "Phone," "DCIM" and then "Camera."
Touch "Disconnect Storage From PC" before detaching the USB cable.
Now, to use the audio file as ringtone, follow these steps:
In Idle mode, press Menu ➔ My Stuff ➔ Audio and press Select. Select a tone and press Options then choose Set as to set the selected tone as a caller ringtone.
Hope that helps!