I see that @Siofra_Strega has already got you started with a few links to tutorials. That’s awesome! That first one has more than 10 (I think?) different tutorials written by the moderators to help you use the forum. The one you’re looking for in regard to your name is this one → 📛 How to Change Your Name and Username on Spells8
As for replying to new topics, the Discobot tutorial is going to be the easiest place to learn how to do that. But a quick rundown for replies in case you haven’t done the tutorial.
At the bottom of a topic there should be a bar with buttons kind of like this one (you won’t have the little wrench icon)
You’ll want to click or tap the one that says “Reply”. If that isn’t there, you may want to check your subscription and see if you have an active Spells8 subscription. Only members can post replies and new topics in most of the forum.
If that doesn’t work, I’m sure @Francisco will be able to help!