There is currently no public API for this. You will have to apply for the Alpha here:
Currently, businesses can create a Shop section on a Page via self-serve Page publishing tools or through select third party eCommerce platforms like Shopify. We're now expanding our alpha test to additional third party eCommerce platforms. Through this API, platforms can offer their merchants the ability to sell products right on their Facebook Page via the same tools they are using to manage their eCommerce business.