// Add to functions.php theme support for Featured Images if your theme does not already include it.
if (function_exists('add_theme_support')) {
    add_theme_support('post-thumbnails');
    add_image_size('index-categories', 150, 150, true);
    add_image_size('page-single', 575, 200, true);
}
 
Call image using timthumb from a page or post by adding to page.php, single.php, home.php or index.php.
 
 <?php if (has_post_thumbnail( $post->ID )): ?>
   <?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' );  ?>
   <img class="featuredImage" src="<?php bloginfo('template_directory'); ?>/timthumb.php?src=<?php echo $image[0]; ?>&w=576&h=200&zc=1" alt="<?php the_title(); ?>" />
<?php endif; ?>
 
CSS
Note: image tag has the class .featuredImage. Style as needed:
img.featuredImage{border: 2px solid #ccc;padding: 10px;}