Go to https://rating-widget.com and click the 'SIGN IN' top menu option and select 'Create Account' in the popup box. Complete the 'Create Account' form and submit. You will receive an email asking you to verify your new Rating-Widget account. Once you have verified you email, log into rating-widget.com and click the 'ANALYTICS' menu option. In the lower right side of this page will be your account details. Copy your Rating-Widget ID and Public Key data.
Download and Install the jRatingWidget plugin and go to this location within your Joomla! installation;
Extensions->Plugins->Content - jRatingWidget
Paste your rating-widget.com ID and Public Key into the plugin settings, ENABLE the plugin and SAVE. At this point EVERY Joomla! or K2 article you have published on your site will have jRatingWidget. You'll want to go back into the plugin settings and EXCLUDE what Categories, Articles or K2 Items you wish NOT to use.
FYI: This plugin is 'Article Title Specific'. With this, each article using the jRatingWidget system is completely independent from one another. Ratings received for a specific article do not effect the ratings of your other articles. This is most helpful for Blog pages.