How to enable emojis in iOS 7
If you're jealous that all your friends are texting poop emojis to each other, you can soon join the fun.
Open settings on your iPhone

Click on General

Click on Keyboard

Click on Keyboards

Click on Add New Keyboard...

Scroll down to find Emoji and click on it

Clicking will automatically add Emojis to your keyboard. You don't need to save anything.
Open your Messages app and test it out
