How to Add Thumbnails to the Blog Page

[tutorials]

Open page_blog.php and place

 <a href="<?php the_permalink() ?>" rel="bookmark"><img class="thumb" src="<?php bloginfo('template_directory'); ?>/tools/timthumb.php?src=<?php echo get_post_meta($post->ID, "thumb", $single = true); ?>&amp;h=<?php echo get_theme_mod('archive_thumb_height'); ?>&amp;w=<?php echo get_theme_mod('archive_thumb_width'); ?>&amp;zc=1" alt="<?php the_title(); ?>" /></a>
                        <?php else: ?>
                        <?php endif; ?>

immediately before

 <?php the_excerpt();?><div class="clear"></div>

This will create a thumbnail the same size as the thumbnail selected for the Category Archive pages.