How can I add an article to a region?
By default drupal don't let you do this , you should achieve it with this two solution


use nodeblock



  This module allows you to specify content type(s) as being a block.
  This allows the content managers of the site to edit the block text
  and title without having to access the block administration page.
  Users only need edit access to that node in order to edit it.
  
  We advice you to use this module together with Node Level Blocks or
  Block Reference module.
  
  It is very handy to create a simple block content type and enable this
  content type for blocks and use these in place of the normal 'add
  block' functionality.



Achieve it by views block,I mean create a view, get result of it with what you want ,then save it as block ( I mean create block view), then put the block in the region you want.