Hi Cyril,
you can put something like this in functions.php:
register_sidebar(array('name'=>'Header Sidebar',
'before_widget' => '<div class="widget %2$s">',
'after_widget' => '</div>',
'before_title' => '<h3>',
'after_title' => '</h3>',
));
and then in header.php at the end of file add this:
<?php dynamic_sidebar( 'header-sidebar' ); ?>
Now you can drag widgets to header sidebar and they will show.
For the second sidebar, it’s the same procedure, and you would need to put call for sidebar in sidebar.php file, right before this <div class="clearfix"></div>
.
I’m not sure what you’re trying to achieve, why would you put sidebar there?