doc: Add instructions for local_settings.py

README.md

@@ -60,7 +60,31 @@ The official Django documentation for this [can be found here](https://docs.djan
 ```
 
 ## Developer guide
+### Instance configuration
+Each installation of VIPSWeb can be customized in several ways
+* The page title
+* Site owner/URL
+* Languages
+* Time zone
+* Point in time (for demoing out of season)
+* Which backend servers (instances of VIPSCoreManager and VIPSLogic) to use
+* Which organization(s) to show data from
+* Front page map configurations (center, zoom and height/width)
+* Which news message types to show on the front page
+* The menu items in the page header
+* The menus in columns below the map
+* Text in the footer
+* Settings for the date picker
+
+This is done by making a copy of `local_settings_sample.py` to `local_settings.py` and customizing it. `local_settings.py` is ignored by Git.
+
+
+
 ### Showing a new model in the detail page (forecasts app)
+The VIPSWeb app has the tools to display results from model calculations. It fetches the data from the VIPSLogic backend. Each model has its own characteristics, and VIPSWeb needs to be told how to display the results from each model.
+
+![Detail view of results from an Apple scab model forecast](./docs/illustrations/detail_page.png "Detail view of results from an Apple scab model forecast")
+
 This has to be configured in the admin section of Django. Log in as administrator, or [create one](https://docs.djangoproject.com/en/3.1/intro/tutorial02/#creating-an-admin-user) if you haven't already.
 
 #### Add result parameters for the model