how to enable comments for content type in drupal 8?

To configure comment settings on a specific content type:

  1. Navigate to the Content types administration page (Manage > Structure > Content types or
  2. Find the content type you want to enable and click the "Edit" link.
  3. Click the "Manage Fields" tab.
  4. Add a Comment field. Click "Edit" next to the Comments" to edit the comment settings. 
  5. Here you can specify several different settings

  Configure a label text, Help text, Default Value setting for new content, Threading, Comments per page, Show reply form on the same page as comments and Preview comments