how to put music on mp3?

hi, =] I bought my daughter a dxg-305v 5 in 1 digital camera. It has an mp3 but I have no idea how to put the music on it. The instructions say : Only song files in the mp3 format can be played on the mp3,once the songs are in mp3 format,they can be transferred onto the mp3 folder on the camera. How do you get an mp3 file,and how do you save the music onto the file? Please help. I would appreciate it. Thank you.

Reply