Added Usage to Snippet Header

Author: sbassah

gp-read-only/gpro-disable-for-admins.php

@@ -6,6 +6,11 @@
  * Disable the Read Only property on fields for Admin users. 
  * This is useful when wanting to allow administrative users to edit fields that non-admins should not be able to edit.
  *
+ * Usage:
+ *
+ * 1. Install this code as a plugin or as a snippet.
+ * 2. Add the `gp-read-only-except-admin` CSS Class Name to field's Custom CSS Class setting.
+ *
  * Plugin Name:  GP Read Only — Disable Read Only for Admins
  * Plugin URI:   https://gravitywiz.com/documentation/gravity-forms-read-only/
  * Description:  This snippet allows you to disbale the Read Only property on fields for Admin users.