We have covered the built-in Emoji support in OS X Lion. Turns out that iOS 5 has the same Emoji characters for you when text is just not enough. In order to enter Emoji characters in iOS 5, you need to add the Emoji keyboard.
From Settings app, go to General > Keyboard > International Keyboards > Add New Keyboard. Look for “Emoji” and tap on it to add the keyboard.
Once a keyboard is added, it can be accessed from the globe icon on the keyboard during text editing. Each tap on the globe icon will toggle among the added keyboards from the Settings app.