How do I get my free pizza with Buy One Get One Free?

If a takeaway is offering The Buy One Get One Free deals on Pizzas, it will appear under the Specific Offer Category on the menu ( e.g Buy One Get One Free, Buy 1 Get 1 Free, BOGOF, etc). 

You need to add two pizzas to your cart and the cheaper pizza will be at no cost. Here's an example of how it would appear on the cart.