I'm not sure if this is the best way but I highlight and copy the text and then go into the text/reply box. I type in [QUOTE} [/QUOTE} (but use the ] bracket on both sides) and then paste the quote between the QUOTE tags. If you want to make the inside words bold, you can put [B}, then paste the quote and then type [/B} after the quote (again, using the [ ] on either side).
Is that clear or did that confuse you more?