Use the quote button when writing a post and paste text in between the code it gives you.
OR the long way....
Hit quote on the first post you want to quote and copy all the text in the box, then go back to the thread page and press quote on the other post you want to quote and paste the text from the first quote at the top of the box. The write what it is you want to write. Just make sure you're not writing
in the quote box
Happens to me lots
*hugs*
xoxoxo