Your custom sidebar can also be shown on Posts. To change the sidebar settings for Posts, go to Appearance > Customizer > Posts.
You can either choose to hide the sidebar completely, or if it is shown - then you can control its positioning:
The sidebar can be shown either below the featured image, or next to it.
- If you choose not to display a sidebar on your posts, the content area will have a larger margin and will be aligned to the center of the viewport.
An example of a Post without a Sidebar can be viewed here.