Tranferring data from computer to LG Shine

Hello,
I've just gotten a LG Shine CU720 and have been trying to add some audio files from my computer to the phone. Mainly trying to add ringtones. I can save voice recordings, as AMR files but they won't work as ringtones. I bought a USB cable for it and tried that, starts to connect as a Music Sync, then disconnects because there is no memory card for the phone. Do I need to purchase a memory card just to connect to my computer? I'm running windows XP. Any help is appreciated...

i had to purchase one and use the memory card adapter to upload music however it wont let me use it for my ringtone

Ringtones must be smaller than 300kb and shorter than 25 seconds. MP3 works fine as rintone.