Run the InitializeOAuth choreo, specifying the Client ID and Client Secret from the app you registered at 23andMe. 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 23andMe 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 23andMe API.
When your access token expires, you can use the RefreshToken Choreo to generate a new one. Note that the 23andMe access token expires after 1 day.