Getting a ring tone from my computer onto my LG Rumor?

[Oskilator]

I recently got an LG Rumor and I wanted to get a custom ring tone on it. I have a USB cord and I can hook it all into my computer, and it's connected properly because it says my phone's charging. But I can't seem to exchange anything from the computer to the phone or vice versa. Help?
I already have the song I want, I just can't figure out how to get it onto the phone.

I don't have internet on my phone, just text messages.

[carrot]

I use Myxer.com But if you want to make COSTOM ringtones, you have to have the music ripped on your computer. So if you have a Kings Of Leon cd and you like the chorus of there one song, then you simply rip it onto your computer, go to myxer, then click make your own. then you will upload the photo and it will tell you what to do from there.

Hope this helped!