Samsung YP5 Mp3 Player - When i first bought from...

Question

when i receive the mp3 player, i long pressed the power button to switch on the player but i wonder why it ddn't work. then i tried plugging it on the USB to the computer the player were raise to life. Then i can play now songs to the player but when i pull off the USB from the computer to my player, the mp3 player switch off... i even tried connecting the USB to the computer for 5 minutes and still when i pull of the USB it's still switch off. How will i charge my mp3 player???