Begin by typing a key word or words from the previous post in the Search box on the blue menu bar at the top right of every page.

If you find too many matches and you know extra info such as who the poster was or whether the word you're looking for was a thread title etc etc You can narrow your search down by using the Advanced Search option

If a match for your search is in a Large thread (multi pages)
Click on the thread in your results and then use SEARCH THREAD on the grey menu bar at the top of the page and type in your search word/s again it then lists the exact posts that your search word or words were mentioned in for you to simply click on and read

I hope that is not too confusing - it is about a simple as I can make it