A good starting point is the web service examples, here: https://gitlab.com/groupbc/webservice-examples/ 
This repository gives walkthroughs of setting up basic authentication and other simple tasks using the BCDE API to use as a starting point for your own applications.

For full documentation of the endpoints available on your version of BCDE, including the names of the endpoints and the keys each endpoint provides, you can use the internal web service documentation. You will need to have a user account for the server in question. After you have logged in you will be able to get to the documentation using this link: https://[SERVER URL.com]/bc/bc.cgi?op=web_service_documentation (where [SERVER URL.com] should be replaced with the URL of the BCDE server you are logged in to).

Examples of the outputs from endpoints can be seen in the Newman documentation which is available for all using this link: https://[SERVER URL.com]/pub/ws_ref_docs/ws_api_reference_documentation.html (where [SERVER URL.com] should be replaced with the URL of the BCDE server you are logged in to).