You can't. You need some kind of back end to generate the search results. You could use a free service, but it won't be on your website.
You can create a hack for it, it just won't be pretty. Have a search form. Let the action be results.php (that part will need to be dynamic). In results.php, do something like this: $q = $_GET['inputname']; if (eregi($q, SOME TITLE OR TERM)) { echo "<a href='linkhere.html'>LinkName</a>"; } etc, etc, etc for each of your pages. PHP: It will work, but will be very time consuming.
Google Custom Search @ http://www.google.com/coop/cse/. I use it on several sites with excellent results. Easy to integrate and it works.
Google custom search is the best option - it works and looks decent since people are probably used to Google search results