Just look around and follow the catagories when posting. 'Post reply' or 'Post new message' buttons are right there for you. As for friends, etc. I know about everyone here and have never added a friend. I would have no idea if anyone has ever added me.
You can see what's going on at the moment by looking at the 'recent threads' just to your right >>>
I think most of your questions will be answered just by hanging around. You've made an excellent start.