Vanguard has several widgetized areas where you can add widgets to. The following image describes what these areas are and where they are applied:
As you can see in the image above, there are a total of 9 widgetized areas in the theme, and all of them can be hidden or replaced with your own custom created sidebars (Main Sidebar can't be hidden). This is possible for every page, post and portfolio item.
Replacing or hiding a sidebar in a page, post or portfolio item is as easy as editing them and customizing a few fields.
As an example, to replace the main sidebar with a custom created sidebar and at the same time hide the footer widget columns in a page, just edit the page and click on the option Sidebar in the Vanguard Page Settings: