Apple iPhones have native support for emojis, and it's easy to add an emoji keyboard to your iPhone. Here's how to do it:
Open the "Settings" app
Navigate to "General" > "Keyboard" > "Keyboards"
Tap "Add New Keyboard"
Scroll through the languages and choose "Emoji"
That's it - you've successfully added the emoji keyboard to your iPhone! Just tap the "globe" icon to switch to the emoji keyboard to add emojis to your messages on any app, and then tap it again to return to your regular keyboard.