Just go to the "user cp" tab find "edit profile pic. And upload pic there.
I think it has to be 800x600 pixels, but it should tell you if the pic is too large. Good luck! And welcome to the forum.
Check out the rules and stickies section. And do a search for things you are interested in at the google search at the bottom of the page. The search bar at the top for some reason does not turn up as much.