1. Click the Website from your admin interface dashboard.
2. Click the Navigation button.
3. Now find the Shopping Cart "page" with you site list and un-check the Active field.
4. Don't forget to Save your changes!

To turn the Shopping Cart on again, you simply re-activate this same field.
For more detail on activating your shopping cart from scratch though.. please check out this lesson in our Getting Started Guide -
http://helpdesk.photomerchant.net/entries/268323

- Done! -