When you are in the reply page to a thread scroll down to the previous posts. On the right side of the post block there is a button that says "Insert Quote". That will insert that quote wherever your cursor is in the reply box. Can add as many quotes as you want!
You can also use the "quick reply" at the bottom of the page. If you click on the "quote" buttons next to each post, it will automatically put the text in the quick reply box. clicking another quote button will add it in the box after the first one.