If you want to refer to a specific post, all you do is go to their post and in the upper right hand corner is a box that says QUOTE.
You click on it. It will have a bunch of jargon and then the person's post. You can delete out sentences that don't pertain to what you want to quote, and then you just write below it. Then, after you spell check, you hit post and the quote will be in blue and your reply will be below it.
If anyone has more advise about "quotes" please feel free to reply to this post or Quote it.