how to add pages list on parent page

Use the child_of parameter with the template tag, wp_list_pages().

mmm I am confused Can you post any example for it?

You’ll need to create a Page Template and in that template, you want to put something like this to list the children of a page:

<?php
wp_list_pages('child_of=6'); ?>

The above lists child pages of Page ID 6.

Resources:
Template Hierarchy
Stepping Into Templates
Stepping Into Template Tags
Editing Files

I have created a new page template bios.php
and the code on the page is:

=============================================
<?php
/*
Template Name: Bios
*/
?>
<?php get_header(); ?>
<!– Container –>
<div class=”CON”>

<!– Start SC –>
<div class=”SC”>
<?php include (TEMPLATEPATH . “/menu.php”); ?>

<?php
wp_list_pages(‘child_of=1263’);
?>

</div>
<!– End SC –>
<?php get_sidebar(); ?>

<!– Container –>
</div>
<?php get_footer(); ?>
=============================================

and now what I need to do?
DO I have to create page and subpage? if so then How the page template would apply on created page?

You do Manage->Pages and edit that page and assign the Page Template.