Add Left Nav to new page

1. Open the page in SharePoint Designer 2010.

2. Go to the 'style' tab in the ribbon, on the 'master page' section, click on 'Attach' and attach the custom (or default) master page:

3. Afterwards, you should see something like this:

  The place holder for left nav:



4.  Select the PlaceHolderleftNavBar, click on the arrow and select 'Default to Master's content'.  The page should now show the left nav: