Step 1

I take a look in index.php. It displays:

<?php
/* Short and sweet */
define("WP_USE_THEMES", true);
require("./wp-blog-header.php");
?>

Step 2

After looking at this code I could see, clearly, there was no statement to restrict what category to show, which was what I wanted. So I checked in the Administration>Categories section in the Administration part of my site to find out the category ID of the category I wanted to just show on my index.php in my Wordpress installation root, the category ID was ‘2?. I changed index.php to the following and uploaded it to my webserver:

<?php
$blog = 1;
if (!isset($cat)) {
$cat = "2";
}
/* Don't remove this line. */
define("WP_USE_THEMES", true);
require("./wp-blog-header.php");
?>