By participating in the discussion.
There are no limits to membership. So, since we've already chosen the book,
Sylvie and Bruno, for this month, just read it and join the discussion (Which will start on the 20th with a new thread in this sub-forum.)
Also, you might want to follow along in the
Lit and MR Book Clubs -- the way forward thread. We're currently working to define a new club that will take the best of both existing clubs and end up with an all new entity here.