Looks like you haven't created the main sidebar yet. Do it now by creating the following page: sidebar

Once you've created the page, just add an unordered list of links to create the navigation i.e.:

  
* [[link 1]]
* [[link 2]]
* [[link 3]]

You can also use one of the many available index plugins.

For further information about sidebars refer to the template documenation.