Custom Notification in WP Admin

admin-notification.php

<?php
//add custom notification in WP Admin
function general_admin_notice(){
	global $pagenow;
	if ( $pagenow == 'post.php' ) {   // add/edit pages/files as required
    //add any custom message here
		$current_user = wp_get_current_user();
		$user_name = $current_user->user_firstname;
		echo '<div class="notice notice-warning">
             <p>Hey <strong>'. $user_name . '.</strong> You are awesome!</p>
         </div>';
	}
}
add_action('admin_notices', 'general_admin_notice');
?>