How can I get the new emojis on my iPhone?

Emoji are contained in iOS updates. If you have updated your iPhone to the latest iOS, then any new emoji that have been released with that iOS would be on your device. The latest emoji release was iOS 15.4.

Update your iPhone to iOS 15.4.

See -> Use emoji on your iPhone, iPad, and iPod touch -> using emojis on your iPhone

See also -> iOS 15.4 should make available new emojis.