At the bottom of the right hand side of the message box is a little box saying 'quote' in it. If you find the quote you want and then use that little box at the bottom of the members message you wish to quote from it will change the page to 'reply to thread' the quote will be attached to the message. If you want to get all complicated there is multi quote - if in doubt try previewing your message to get an idea if you have done it right.