How to use the onramper apache?

Question

PHP

Friends, let my open question seem stupid, but I really don’t understand how the API does not work in general, since I worked with Bitrix API and Robocas and others. But in the case of this api, I found a lot of questions for myself.

The documentation also pours fuel on the fire. Tell me can someone worked with this api or similar. I will be glad for any help