How do I get the radio to work on my iPod nano 6th gen?

I have synched my Nano & have music...I have plugged in the earphones, but nothing happens with the radio. I've read the support article about the FM radio, but I don't have any of the radio controls shown in the article--all I have is the radio icon and the Now Playing icon, and when I tap the Now Playing icon, it shows what music is playing, not radio controls. Help!