Instructions
Turn off the Xbox. Connect the USB flash drive to it, and turn it back on.
Select the "My Xbox" menu. Scroll to the right and select "System Settings." Select "Memory."
Select the "USB flash drive." Scroll down and select the "Music" subfolder. Select the song that you want to put on the Xbox 360. Select "Copy." Select the "Xbox 360 hard drive" as the transfer device. Repeat this step until you have all of the music you want on the console.