Run the InitializeOAuth Choreo, specifying the Client ID from the app you registered at Uber and the desired Scope. The InitializeOAuth Choreo will return an authorization URL and a callback ID (required for the FinalizeOAuth step).
Open a new web browser, navigate to the authorization URL returned by the InitializeOAuth Choreo, and click "allow" to grant the app access to your Uber account.
Run the FinalizeOAuth Choreo, specifying the callback ID returned earlier by the InitializeOAuth Choreo, to obtain an OAuth Access Token that can be used to access the Uber API.
When an Access Token expires, you can run the Uber > OAuth > RefreshToken Choreo providing the Client ID, Client Secret, and Refresh Token (also returned during the OAuth process) to retrieve a new Access Token.
Note: if your application only needs to use Choreos within the Projects and Estimates bundle, you'll just need to authenticate using your ServerToken. For Choreos within the User bundle, you are required to authenticate using OAuth credentials.