Update README

README.md

@@ -97,6 +97,17 @@ Finally, you can start the development server:
 $ poetry run ./manage.py runserver
 ```
 
+### Extending the settings
+
+If you want to extend the settings while doing local development with poetry,
+you just need to set the `DJANGO_SETTINGS_MODULE` environment variable to point
+to the new settings file, e.g. to run the server using the `sample_settings.py`
+file:
+
+```shell
+$ DJANGO_SETTINGS_MODULE=steering.sample_settings poetry run ./manage.py runserver
+```
+
 ## Data Model
 
 A visualization of the data model can be generated using the [Graph Models