in order to retrieve the cart information, you need the following code in your page at or near the top of the page, (before the <!doctype.. statement)
//WA eCart Include
where CARTNAME is the name of your ECart object instance
where you wish to dispay your cart quantity, (in the masthead ?), add the code...
<?php echo $CARTNAME ->TotalColumn("Quantity").' items in cart'; ?>
you may find it easier to add quick cart from the eCart display manager first, as this puts in all the code you need, then adapt what is displayed according to your requirements