To add a new Top-level menu to WordPress Administration, use the add_menu_page() function.
//////neha jaiswal///
<?php
add_action('admin_menu','wpac_register_menu_page');
function wpac_register_menu_page()
{
add_menu_page('WPASsystem','WPAC Settings','manage_options','wpac-setting','wpac_settings_page_html','dashicons-admin-plugins',15);
}
function wpac_settings_page_html()
{ $content='';
$content.="<h1>welocome</h1>";
$content.='<form method="post">
<h1>Contact Us</h1>
<div class="info">
<input type="text" name="name" placeholder="Full name">
<input type="text" name="email" placeholder="Email">
<input type="text" name="number" placeholder="Phone number">
<input type="text" name="Website" placeholder="Website">
</div>
<p>Message</p>
<div>
<textarea rows="4"></textarea>
</div>
<button type="submit" href="">Submit</button>
</form>';
echo $content.='<button><a href="https://www.w3schools.com">absgfs</a></button>';
}
add_shortcode('wpac-setting','wpac_settings_page_html');
?>
/////////////// plz visit this site for more details //////
https://developer.wordpress.org/plugins/administration-menus/top-level-menus/