To quote a whole post..
You can use the "quote" button in the bottom right of any post to quote the whole post.
Or to quote part of a post
1~ highlight the text that you want to quote
2~ copy and paste to your posting text box
3~ ensure that the text you want to quote is still highlighted
4~ press the quote box (looks like a cartoon cloud, it's right besides the link button) at the top of your post text box.
You can simply type QUOTE in brackets as Jon says.
For example, but I'm using the word frog instead of QUOTE so it shows up.
[FROG]words you want to quote[/FROG]
It does work