See Product Feed and Cart Transfer Integration.
Web checkout integration allows for a seamless shopping experience in your shopping apps by allowing users to easily transfer the items in the app bag to your web checkout. With the web checkout integration, users tap “Go To Checkout” on the native bag page and the app opens an app web view to display the web checkout page on your website.
It is usually quite easy to implement and carries minimal risk to your deployment.
To set this up on our end, we need to know from you: