You just stuck that code where ever ... I do not know what module you are using but it should have a line like the Checkout/Money Order moneyorder ...

The code would go between the two lines in black:
Code:
      if ((int)MODULE_PAYMENT_MONEYORDER_ORDER_STATUS_ID > 0) {
        $this->order_status = MODULE_PAYMENT_MONEYORDER_ORDER_STATUS_ID;
      }

// bof: Only for Discount Group 2
      if (!IS_ADMIN_FLAG) {
        global $db;
        $chk_discount_group_sql = "SELECT customers_group_pricing FROM " . TABLE_CUSTOMERS . " WHERE customers_id = '" . $_SESSION['customer_id'] . "'";
        $chk_discount_group = $db->Execute($chk_discount_group_sql);
        if ($chk_discount_group->fields['customers_group_pricing'] != 2) {
          $this->enabled = false;
        }
      }
// eof: Only for Discount Group 2

      if (is_object($order)) $this->update_status();
NOTE: the Zen Cart Free Charge freecharger ONLY will work when there are NO chargers on the Order and NO shipping as in a totally FREE Order ...

It does not MAKE the order free ... it shows *because* the order is Free ...