How to get my iphone to play on tv?

Ok so I have an iphone 4 and an aux to av cord that I want to use (headphone to the three white, yellow, and red ends that go into a tv, just in case I said that wrong). I know there used to be a setting that would let you watch video on TV. I've looked and I can't find any setting. I'm running IOS7 so that might be a problem. Anyway answers are much appreciated

Merry Xmas. You may refer to this step by step guide, it's about how to connect iPhone and iPad to TV, it works pretty well for my iPhone 4s.

http://www.reviewstown.com/how-to-connect-ipod-iphone-ipad-to-tv.html

Hope it helps. Contact me if you have any other question.