I am assuming you can retrieve the data from your db for display on your main page, well using the same logic you can display search results based on keyword search by chaning your query a bit. This type of query will depend on how indepth you want your search to be. Do you want to just try and match what the user has typed in exactly, if so, it is very simple to do. I will show you this example and if you want to be bale to search on any word they type, let me know.
First you should have a searchbox somewhere
if ($searchwords) {
$result = mysql_query("SELECT * from newstable where thefieldthatholdsnewstext LIKE '%$searchwords%'");
//Process $result as normal
}
<form method="post" action="<?php print $PHP_SELF; ?>">
<input type="text" name="searchwords">
<input type="submit" name="submit" value="Search">
</form>
