Natured includes the option to show the Related Posts section when viewing the full post.

screenshot demo of the full post Related Posts feature
  1. Go to the Appearance > Customize > Post Options.
  2. Look for the Display Related Posts setting and check the box to show it.
  3. From the Display Related Posts By dropdown, choose the method to use.
  4. Click the Publish button.
screenshot for the display related posts by method setting