How to set up Google+ authorship in Drupal 7
The easiest way is with the Metatag module:


  The Metatag module allows you to automatically provide structured
  metadata, aka "meta tags", about your website. In the context of
  search engine optimization, when people refer to meta tags they are
  usually referring to the meta description tag and the meta keywords
  tag that may help improve the rankings and display of your site in
  search engine results.


After you install/enable the module, you can edit the metatags at admin/config/search/metatags  The Google+ Author is under Advanced.