Emoji aren’t built into WhatsApp for iPhone. However, emoji can be used on iPhone by using the emoji keyboard. Contact Apple support to learn how to enable the emoji keyboard.
Once the Emoji keyboard is enabled, you can access it by tapping the Globe or Emoji icon on the keyboard.
Note: Apple regularly introduces new emoji in new iOS versions. Please make sure you use the latest iOS version to have access to the latest emoji. Instructions for upgrading your phone's software can be found on the Apple Support website.