update README.ms for custom model

README.md

@@ -58,15 +58,12 @@ This is the contents of the published config file:
 ```php
 return [
     'enabled' => false,
-    'models' => [
-        'field' => \SolutionForest\FilamentFieldGroup\Models\Field::class,
-        'field_group' => SolutionForest\FilamentFieldGroup\Models\FieldGroup::class,
-    ],
     'table_names' => [
         'fields' => 'advanced_fields',
         'field_groups' => 'advanced_field_groups',
     ],
 ];
+
 ```
 
 ## Usage
@@ -158,6 +155,19 @@ $panel
     );
 ```
 
+### Custom Models
+
+This section allows you to customize the model used for field groups in the Filament Field Group package. By replacing the default `FieldGroup` model with your own implementation, you can extend or modify its behavior to suit your application's needs. 
+
+To do this, use the `replace` method from the `ModelManifest` facade, specifying the original model and your custom model. Here's an example:
+
+```php
+\SolutionForest\FilamentFieldGroup\Facades\ModelManifest::replace(
+    \SolutionForest\FilamentFieldGroup\Models\Contracts\FieldGroup::class,
+    Your\Models\FieldGroup::class
+);
+```
+
 ## Testing
 
 ```bash