I am very new and very dumb. 
Please give me directions that are /srs
I will most likely not detect sarcasm and struggle without explicit instructions. 
I am on mobile currently. I'm supposed to be asleep. I am not asleep. I'm hyperfixated on new internet place.
I haven't quite figured out the UI yet but it might just not be optimized for mobile. Is there an app or should I just wait until I get back on my PC?
Welcome! Personally I use the mobile site, and there's no mobile app for Hexbear specifically. However, Hexbear is part of a network of sites called Lemmy that can optionally federate with each other and see each other's posts/comment on each other's sites. Which instances federate with each other is a whole bunch of drama, but I digress. There are some Lemmy apps that you can use to browse Hexbear, but we have some custom features like pronouns and the emoji picker that may or may not be supported.
Jerboa is a popular Lemmy app, I think
Jerboa is by far the best mobile app. I had to set my pronouns on the mobile website, and it shows up in Jerboa after that.
I use Thunder, on which I can change my display name. Are there still some that can’t show Hexbear emojis?
You'll be able to view the emojis fine because they're just linked images. It's just that we have a lot of them, and there are features that will allow you to search for them and automatically add them into your posts/comments that don't work in (most? any?) of the mobile apps
There were some apps when Hexbear first federated that didn’t display them or displayed them poorly, messing up the formatting. I was on Memmy, but switched to Thunder because Memmy can’t handle the formatting (I just checked, it still can’t).
I remember the days of the Giant Emoji