Gravity Forms plugin: How to use “gform_editor_js” action hook? [closed]

You can either place the code snippet in the theme functions.php file or in a custom functionality plugin: http://justintadlock.com/archives/2011/02/02/creating-a-custom-functions-plugin-for-end-users

Edit:

To enqueue custom scripts on the edit page you should use admin_enqueue_scripts e.g.

add_action( 'admin_enqueue_scripts', 'my_jquery_function' );
function my_jquery_function() {
    if ( rgget( 'page' ) != 'gf_edit_forms' )
        return;
    wp_enqueue_script('mytest1', get_stylesheet_directory_uri() . '/assets/javascripts/mytest1.js');
    wp_enqueue_script('mytest2', get_stylesheet_directory_uri() . '/assets/javascripts/mytest2.js');
}