Added documentation

docs/index.rst

@@ -153,6 +153,32 @@ setting to ``False`` and give the users or user groups access to the
 
    The virtual application ``Constance`` among your regular applications.
 
+Custom settings form
+--------------------
+
+If you aim at creating a custom settings form this is possible in the following
+way: You can inherit from ``ConstanceAdmin`` and set the ``form`` property on
+your custom admin to use your custom form. This allows you to define your own
+formsets and layouts, similar to defining a custom form on a standard
+Django ModelAdmin. This way you can fully style your settings form and group
+settings the way you like.
+
+.. code-block:: python
+
+    from constance.admin import ConstanceAdmin, ConstanceForm, Config
+    class CustomConfigForm(ConstanceForm):
+          def __init__(self, *args, **kwargs):
+            super(CustomConfigForm, self).__init__(*args, **kwargs)
+            #... do stuff to make your settings form nice ...
+
+    class ConfigAdmin(ConstanceAdmin):
+        form = CustomConfigForm
+        change_list_template = 'admin/config/settings.html'
+
+    admin.site.unregister([Config])
+    admin.site.register([Config], ConfigAdmin)
+
+
 More documentation
 ------------------