When the user is satisfied with their shopping cart and are ready to check out, you'll make an ajax request to our checkout/charge endpoint, where an attempt will be made to process the payment. You will then be returned a redirect url which leads to the order receipt if successful, or the payment confirmation page if required.
The entire payment confirmation process is handled out of the box. It even renders a nice error page if the confirmation fails. All you need to do is make sure you redirect to the returned url when the checkout/charge call is done.
We currently support accepting payments through Stripe out of the box. To learn how to implement it, see the Stripe guide.