First, welcome back! I'm glad to hear your health has stabilized.
Like the others said, you weren't doing anything wrong, but pretty much the only way to integrate anywhere, not just here, is to get involved with discussions and games and whatever else is going on at a given time. That's how we get to know each other. {= )
Jumping in head-first can be scary, though, so to get a sense of how things work on the Board, I recommend reading stuff on the Board. Read everything. Read posts you wouldn't normally think of reading, because you never know what might come up as the thread goes on. We are incredibly prone to tangents and silliness around here.
I'm afraid that's pretty much all there is to it, though: reading and writing. If you didn't come here expecting to do lots of both, especially the first, that's the bit you'll have to work on to improve. You'll never catch on to how we do things if you don't observe others interacting for yourself, and since that pretty much all happens in text, the only way to observe is to read.
Also, speaking for the wiki, there are less-than-random ways to go about learning over there. For instance, if you read the main page, you'll find many particularly handy links listed. For another thing, there's a blue menu bar across the top of the wiki, where there are more handy links. Some of them are the same ones, and you can assume those are important, and some aren't, but those are good to know, too.
When you feel ready, a great way to start interacting would be to leave reviews of new missions for their authors. Being new doesn't make your opinion of a story any less valid, and constructive feedback is always gratifying for the author. Plus, we all like talking about our characters, so commenting about them is a good way to strike up a discussion with someone new. {; )
I hope that helps.
~Neshomeh