This is a dumb question, but I have looked all over the site trying to find out how a poster highlights part of a reply in a blue box. Any help in this area would be greatly appreciated.
Hit the Reply with Quote button and then delete some text whilst being careful not to delete the tags - those square bracket with the QUOTE words inside.
Alternatively you can highlight then copy/paste the part you want to quote into the reply box. Then, while still highlighted, hit the button.