Rich Snippet is automatically activated after the upgrade. The markup will be added automatically to your posts and pages once they receive at least one vote. All you need to do is to test the markup by following these simple steps:

• Go to your WP Admin Dashboard -> RatingWidget -> Account and make sure your license is Professional or Business. If not, please click the Sync License button.
• Then, vote any of your posts or pages.
• Purge the cache if you have any caching plugins.
• Check the markup by following the instructions here: How can I check that I’ve correctly configured the Rich-Snippets ratings for Google SERP?