To get icons, also known as emoji, for text messages, a user has to enable the emoji keyboard by accessing the Settings menu on his iPhone. After enabling it, he can tap the smiley face icon and select the desired emoji. Alternatively, he can download an emoji app from iTunes.
To enable the emoji keyboard, a user has to tap Settings, select the General option and then tap Keyboard. In the Keyboard section, he needs to tap Keyboards, select the Add New Keyboard option and tap Emoji. This should enable the use of icons in any app that uses the standard iPhone keyboard. Emoji apps allow the use of larger icons and stickers in addition to the standard emoji icons.