All right, there are plenty of resources put out by Discord to help out.
- Beginner's Guide to Discord
- Getting Started on Mobile
- Sending Messages
- Discord Interface Help Articles
- Markdown Text 101
- Sending GIFs on Discord
Additionally, we have a #help channel if you're super stuck and need a hand, although you can probably find what you're looking for by Googling or otherwise searching for the thing you're stuck with and adding discord to your search terms.
Oh, one more thing -- do not worry about "Nitro". Nitro is the paid version of Discord. They can be fairly annoying about trying to encourage you to purchase it. You do not have to do so. You will see a lot of stuff about Nitro, particularly when you first sign up, but don't use it if you don't want to. If you're curious, you can learn more about it here and make an informed decision.
All right, I think that's about it. If you don't have your invitation yet, don't forget to contact us with as much as you can remember from being on your BONC list, back in the day!