Loading music. I just received yesterday the mp3/mp4 player and i'm trying to put music on it but

Question

I just received yesterday the mp3/mp4 player and i'm trying to put music on it but its not working. i have the media player on my computer and when i tried to connect it said that it synchronized and the file device loaded up, but when i go on my player it just reads file empty. can you please explain to me what to do?