Well overall, Smashboards is very active, especially the Smash Bros. for Wii U/3DS forums, so if you're interested, that's the main spot to be at. Some areas are less active than others, such as the Brawl forums and forums that aren't related to Smash, but they still receive a fair amount of activity. The community is very accepting (in my opinion anyway) to both casual and competitive players, so you won't feel left out when it comes to discussion. Whenever you find a thread in a forum that you feel you can contribute something toward, feel free to share your thoughts. Things carry on like a typical forum, just in a different atmosphere, if that makes sense.
Not sure if that was the explanation you were looking for, but feel free to ask other questions about this place if you're curious.
Start with having a look at the
user guide and the
Global Rules.