How to switch off 3G to save battery life on iPhone 6?

How do I switch off 3G to save battery life on iPhone 6?

I think you meant iOS 6. IPhone 5 is the latest iPhone in the market. Go to settings > general > cellular. Here you should see an option for enable 3G data. It is on by default and you can turn it off from here. If you turn it off, your Internet would be considerably slow on the phone.