You've got it right! Just introduce yourself. Welcome to EC! Hope you like it here, and if you have any questions about how things work, don't hesitate to ask. My name's TJ. See you around.
What do you mean? From a technical standpoint, you go to the Forum home, select a category that interests you, and find a thread that interests you. If you're talking about the purpose of the forum, well, people want to discuss things either about the world, themselves, or others. They find the appropriate subforum and make a thread talking about it. Simple as that. Have you ever used a forum before?
Welcome to EC. If you have questions about the "nuts and bolts" of how this forum works admin and the mods are available. Hope that helps.