How do i put music on my samsung gravity without a memory card?

I got a Samsung gravity 3 and i want to put music in it. So, i got the usb cord, but i don't know which one to pick mass storage or pc studio, and i read the booklet for this and it said i need a memory card, but i don't have one. So how do i do this?How do i put music on my samsung gravity without a memory card?
You really can't put mp3s on your phone without first putting them on a memory card. You can generally move or copy them into the phone later, but there's really no way around using a memory card initially. But the cost of memory cards has gone *way* down lately. The ones with less capacity are downright cheap if you go to someplace like walmart or kmart.