/includes/templates/YOURTEMPLATE/templates/tpl_index_categories.php
Code:
<?php if (DEFINE_MAIN_PAGE_STATUS >= 1 and DEFINE_MAIN_PAGE_STATUS <= 2) { ?>
<div id="indexCategoriesMainContent" class="content"><?php
/**
 * require the html_define for the index/categories page
 */
  include($define_page);
?></div>
<?php } ?>
move down below this:
Code:
<!-- BOF: Display grid of available sub-categories, if any -->
<?php
  if (PRODUCT_LIST_CATEGORY_ROW_STATUS == 0) {
    // do nothing
  } else {
    // display subcategories
/**
 * require the code to display the sub-categories-grid, if any exist
 */
   require($template->get_template_dir('tpl_modules_category_row.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_modules_category_row.php');
  }
?>
<!-- EOF: Display grid of available sub-categories -->