Using API -> Pay for order

Hi,
I found the Using API documentation (https://docs.sylius.com/en/1.12/getting-started-with-sylius/using-api.html) with basic steps to work with. The last step is to complete the order. But I can’t find how to pay for the order throw API. Also I found this controller: sylius.controller.payum::prepareCaptureAction. But I can’t find any api calls for it. Do these API calls exist or I should create it by myself?
Any example would be great.

Thank you!