Hey,
If you're using Win XP, plug the bundled data cable into your phone (behind a flap) and the other end into a USB port on your pc. Your computer will then recognise the phone as new hardware. Wait a sec and then go to "My Computer" in the start menu and your LG phone should appear under "Devices with removable storage", just as if you had plugged in an external hard drive.
Double click on the LG phone in that window, then open your "My Music" folder on your pc and click and drag your music into the other window, where there should be a "Media" or "Music" file on the phone.
Hope this helps. I'm a bit rusty as I have gone back to a four year old Nokia after I dropped my Chocolate and b11ggered the microphone!