The free version of the plugin, aka Molongui Authorship Lite, is in the WordPress plugin directory, so it can be installed using WordPress Plugin Search feature.
Just go to your WordPress admin area and:
- Click on Plugins > Add New
- Find the plugin by typing Molongui Authorship in the search bar.
- Once listed on the search results, click the Install Now button.
- Click on the Activate button to get the plugin up and running
Really that easy!