Either open your sidebar.php in a program like dreamweaver or notepad, OR via ftp go to wp-content/themes/name of your theme and chmod all the php files to 777 so you can edit them from your presentation/theme editor in the admin panel. The basic call for pages is

<?php wp_list_pages(); ?>

for more ways of stylizing that check here: http://codex.wordpress.org/Good_Navigation_Links