The Shareaholic plugin for WordPress provides an easy, free, way to add social share buttons to your web site. This video explains how to use it.
It also offers analytics and related posts, but these are not covered in this video.
This is where you can get the Shareaholic plugin: https://wordpress.org/plugins/shareaholic/
This is my post (mentioned in the video) on how to install a plugin onto WordPress: http://geckogullywebsites.com/add-plugin-wordpress-site/