If you are a Mastodon server admin, here's how to add custom emoji to your server:
https://fedi.tips/using-custom-emoji-on-your-mastodon-server
The guide also covers how to clone them from other servers, and how to block unsuitable emoji.
If you're an ordinary user and just want to know how to access custom emoji, here's a guide for you instead:
https://fedi.tips/what-are-custom-emoji-how-do-i-access-them-can-i-add-new-ones
@feditips a good set of pride flags is highly recommended
@feditips If there’s a way to fetch these from a post’s origin server that would be great for reading. Having a list of your server’s supported emoji while composing too (doesn’t have to be, even rather not, a custom keyboard - would like to see the difference from unicode ones)
@ivory @mammoth @MonaApp @IceCubesApp