added docs for registering fields with php

README.md

@@ -92,7 +92,41 @@ Setting the value of this field to "Yes" will show the field group in the WPGrap
 
 ##### Registering Fields in PHP
 
-When registering ACF Fields in PHP, `@todo`
+When registering ACF Fields in PHP, you need to add `show_in_graphql` and `graphql_field_name` when defining your field group.  See below as an example.
+
+```
+function my_acf_add_local_field_groups() {
+
+	acf_add_local_field_group(array(
+		'key' => 'group_1',
+        'title' => 'My Group',
+        'show_in_graphql' => true,
+        'graphql_field_name' => 'myGroup',
+		'fields' => array (
+			array (
+				'key' => 'field_1',
+				'label' => 'Sub Title',
+				'name' => 'sub_title',
+				'type' => 'text',
+			)
+		),
+		'location' => array (
+			array (
+				array (
+					'param' => 'post_type',
+					'operator' => '==',
+					'value' => 'post',
+				),
+			),
+		),
+	));
+
+}
+
+add_action('acf/init', 'my_acf_add_local_field_groups');
+```
+
+Each individual field will inherit its GraphQL name from the supplied `name` tag. In this example, `sub_title` will become `subTitle` when requested through GraphQL. If you want more granular control, you can pass `graphql_field_name` to each individual field as well.
 
 ## Supported Fields