I'm confused why you're confused. A discord is just a chatroom server. Click on the chatroom and type your message in the textbox and read other messages. It has native support for things IRC didn't, like emojis, the ability to upload files, voice chat, etc.

Maybe you joined a discord with too much traffic. But I'm in the most popular discord that covers my entire state and #general can go hours without anyone talking.

If you think its too complicated, maybe you're over thinking things.