About time for a new rear tire I'd say. In my experience, Shinko tires are junk. I'd suggest a Michelin City Grip.
Regarding replies, I'm not sure what you are not figuring out. Did you look at Rob G's reply on your other post (see below)? Just hit "post reply" or "quote" and type your message. Then hit "submit" when you are done typing. It is really no different than starting a "new topic" as you are already doing.