In the black bar that above that starts with "User CP" and ends with "Log out" is a "search" button.
Click on that once and it will drop down a menu...
Click on "Advanced search" and it will open the advanced search window.
Enter in the keyword you are looking for and whether or not you want to only search the titles of the threads or the complete thread.
AND/OR enter the user name you want to use and weather you want to search for only threads STARTED by that user or just that the user had posted in the thread. These are the "drop down" choices for these options.
Then below that, in "Search Options" you can click on the forum or sub forum you want to look in as well as a date spread for the threads you are looking for.
Since the older threads will take some time to re categorize. Searching under the main heading EG..."Polaris" will look in all the sub forums and the yet to be categorized general Polaris listings.
Hope this helps.
MH