Featured Products is a widget. Inserting content here is tricky, because there is no real hook. But what the widget does is a simple call to WP_Query, and here we can use the action loop_start. We just have to make sure to find the correct loop_start, because there are probably many more on each page.
So first create a function for the description:
function print_woo_featured_products_desc()
{
remove_action( current_filter(), __FUNCTION__ );
echo 'This is my description.';
}
This function removes itself from the current filter (loop_start) and prints your description. Now we have to activate it somewhere:
add_action( 'woocommerce_loaded', function() {
add_filter( 'dynamic_sidebar_params', function( $params )
{
if ( $params[0]['widget_name'] === __( 'WooCommerce Featured Products', 'woocommerce' ) )
add_action( 'loop_start', 'print_woo_featured_products_desc' );
return $params;
});
});
Explaining what happens would take too much time. And I did that already:
- Add class to before_widget for all widgets with a dropdown and a counter
- Programmatically add widgets to sidebars
The related products are a template. Just copy woocommerce/templates/single-product/related.php to your theme into /themename/woocommerce/single-product/related.php, and add your description after
<h2><?php _e( 'Related Products', 'woocommerce' ); ?></h2>