Accessories

I hooked up my i875 to my USB port and it it seen under device manager as a modem. A diagnostic test shows all is working fine. My question is, how do you transfer data , i.e. ringtones, to the phone via the USB port? By the phone being shown as a modem, of course, it is not an option to store this file to it. I am attempting to add ringers and wallpapers because doing so to the memory card never shows the files on the phone. thanks, in advance.