To get the new Emojis, you must be running iOS 12.1, not 12.0.1.
Apple brings more than 70 new emoji to iPhone with iOS 12.1 - Apple
Go to Settings->General->About->Version, and verify it is 12.1
If it is not 12.1, go to Settings->General->Software Update, and check for an update to 12.1.
Once updated to 12.1 they will appear in the Emoji Keyboard on any app that uses a keyboard.
If you are using a 3rd party onscreen keyboard, the new emojis may not show up. Revert to the default Apple keyboard and check again.