How to add a box note in wordpress plugin page ? top header side.

I have provided a small plugin to do just that. This plugin is based and works like the WordPress Hello plugin.
Just save the script below to a file (e.g. mynotes.php) and place in your plugin folder. You can also edit the plugin name and the functions to suit your desire.
To change the note, just replace the content $notes in the function my_notes().

<?php
/**
 * @file
 * My Note WordPress plugin.
 * Plugin name: My Note
 * Author: Your Name
 * Description: My custom plugin to create notes for admin
 * Version: 1.0
 */
if (!defined('ABSPATH')) die('Direct access is not allowed.');
// 
function my_notes() {
    /** Put our notes here one per line */
    $notes = "Hello, Admin, welcome to my notes. Notes will always show here.";

    //split the notes into lines
    $notes = explode( "\n", $notes );

    //return the lines randonmly
    return wptexturize( $notes[ mt_rand( 0, count( $notes ) - 1 ) ] );

}

// This just echoes the chosen line
function show_notes() {
    $note = my_notes();
    echo "<div id='notes'>
            <h4>My Note</h4>
            <em>$note</em>
         </div>";
}

// Set the function up to execute when the admin_notices action is called
add_action( 'admin_notices', 'show_notes' );

// Create CSS to stylize and position the output
function notes_css() {

    echo "
    <style type="text/css">
    #notes {position:fixed; right:calc(40% - 110px); top:0; line-height: 19px; padding: 12.5px; font-size: 12px; text-align: left; margin: 25px 20px 0 2px; background-color: #fff;
        width:220px; height:auto; box-shadow: 0 1px 1px 0 rgba(0,0,0,.1);}
    #notes h4{display:block; margin:0 0 13px; font-size:14px; font-weight:600; color:#162E43; text-align:center;}
    </style>
    ";
}

add_action( 'admin_head', 'notes_css' );

?>