Most of the themes offer widget area’s in top-bar if that is the case you can simply place the following shortcode in the top-bar/header widget area.
In case your theme does not offer a widget area where you want to display cart summary, Or you will need to edit your theme file (usually header.php) and insert one of the following codes in it an appropriate place.
<?php echo do_shortcode("whcom_op_cart_summary"); ?>
- dropdown: If you want to show cart in theme header in dropdown format.
- button: If you want to show cart in theme header in button format.