Main Menu link to all newsletters and another for Articles
How much I understand go to structure > menu > main menu and click "add link" for Drupal 7 and structure > menu > main navigation for Drupal 8



 and for this, you need to create two views one is for newsletter content type and second is for article content type. You can make the view by going to structure > views > add new view for both Drupal 7 and 8. The view type must be page not block. 



All the pictures are for Drupal 8. If you need more assistance please let me know.