What you do is click on the icon to the right of the quote button on all posts you want to quote except for the last one.
The multiquote button is the one that I highlighted in yellow:
The last post that you want to quote in your series of quotes will require you to click the quote button, and all of the previous posts which you clicked the "double-paper" multiquote icon will show up in the text box as well.
^ Nice. I was going to ask you if you wanted to practice in here, but since you figured it out already I am going to close this thread since the question has been answered. PM me if you need it re-opened for any reason.
^ I was going to mention that, but then figured since they were looking to multi-quote it might be better in a place with multiple posts. Of course they can start a thread and make several posts and then multi-quote themselves. Either way....