If you want to use the Epicollect5 API to get data for a private project, you will have to register your "app" to get authentication details to exchange with the Epicollect5 server.
Go to your Apps page under the Developers section:
Click on the "Create New App" button
Now you can use the generated Client ID and client Secret in your script. Show me how.
Notice you need to register your app only once for a project and reuse the Client ID and Client Secret on your applications.