How to generate my menu in primary location

Hello,

to avoid installing my menu in each pages (sidebar.php, index.php, category.php, etc.), i creat a template part (a php.file) for my menu, for example (i have a twentyeleven child theme, i will change the codes of course):

<?php
/**
 * The template for displaying menu in Twenty Eleven
 *
 * @package WordPress
 * @subpackage Twenty_Eleven
 * @since Twenty Eleven 1.0
 */
?>

<div id="menu">
<ul>
<li>
<a href="http://www.mylink.com/">home</a>
</li>
<li>
<a href="http://www.mylink.com/">about</a>
</li>
<li>
<a href="http://www.mylink.com/">contact</a>
</li>
</ul>
</div>

Then i install the <?php get_menu(); ?> after the <div id="primary"> in each page where i want to show the menu…

I guess i must also make some codes in the function.php, how should i do ???
What else should i do still ?

Thanks for your help in advance !