In your theme folder (eg. wp-content/themes/themename), open the page.php file. Check whether your theme is using the default sidebar. You should see something like this:
<?php get_sidebar(); ?>
Otherwise, some themes have their own defined sidebar. And you might see a line of code similar to this:
<?php include (TEMPLATEPATH . ‘/sidebar1.php’); ?>
If its the 2nd case, just change the path and link to the sidebar.php which should be inside your theme (wp-content/themes/themename/sidebar.php)
