Archive Settings
Go to Appearance >> Customizing >> Design Settings >> Archive Settings.
Choose the archive sidebar from available options.
Choose the archive content layout from available options.
Page Settings
Go to Appearance >> Customizing >> Design Settings >> Page Settings
Choose sidebar from available options for a single page.
Post Settings
Go to Appearance >> Customizing >> Design Settings >> Post Settings
Choose sidebar from available options for a single post.
Click on Related Post OptionĀ to show Related Posts.