How do you do a keyword (alien) search?
Go to Free Republic's main page (click "Free Republic" in the top left corner if you open on the Latest Articles page) and type the keyword into the "Search" box located under that heading stuff. There's a dropdown list on the right of the Search box so you want to make sure you've chosen "By Keyword" for the category of search.
The other choices are useful, too. If you know just a few words of the title of a specific article searching for that with the "By Title" category will dig it up.