This post here might help:
https://permies.com/t/90752/emoji-translation-service#751267. When you make your post, make sure to unclick the "disable smilies" option (it's above the "submit" button). If you're using the "quick reply" option, it defaults to having smilies enabled.
(You can
blame me for why it's hard to figure out what the smilies are here on permies).
Smilies are different than emojis. I'm never really tried to incorporate emojis into my posts, but I think you can copy and paste an emoji and it'll sometimes come across. Not everyone's systems have all emoijis, so sometimes when someone uses an emoji that my computer doesn't support, I just get a mystery character.
I hope that helps!