I wasted quite a lot of time when setting up an App registration to upload documents to SharePoint using REST actions in WEBCON.
Since WEBCON BPS 2025 does not support certificate authentication I had to persuade SharePoint to allow Client id/secret authentication.
Maybe I did something wrong, but I also was not able to use the build in OAuth authentication option. Therefore, I added an example on how to get and use the access token with REST actions.
You can read up on it here: