Below are step by step instructions. Click on pictures below to see them better. Smat quote only works in IE.
Start by opening a post with some replies, like this one.
Start replying by clicking any of the Reply buttons and maybe typing some text.
Below the editor window there is the thread view window. Find a piece of text that you want to quote there. You may need to scroll. Select the piece.
Click the Quote button. Do not click anywhere else or you lose your selection.
Your quote is inserted!
You can repeat the process as many times as you want.