If you haven’t noticed, the sidebar navigation appears on the “Home Page” and on “Pages”, but not on “Posts”.
If you’d like to add the “sidebar” navigation to all of your “Posts”, you just need to make 2 edits in the single.php (/wp-content/themes/default/) page.
First (and this is not even strictly necessary – it just makes the body text “left-justified” instead of “centered” as it is on the Home Page and Pages) change the first “div” from:
Then, to add the sidebar navigation, invoke the following function as the 2nd to last line of code:
It should be just before:
Hope this helps.