Connecting my Macbook Pro to my TV

The other day, I went out and found a MiniDisplay Port to HDMI adapter to help connect my Macbook Pro (Mid 2012) to my TV (24" LG LCD). Everything connects fine, but when I set my TV to the HDMI input, all I see is my Macbook's background. How can I get videos to play on my TV while it is connected to my computer instead of showing my background?