In order for this update to work, you must have a Google+ account. You can use either a personal or business account, but you'll get the most out of this feature by having both.
Next, you'll need to link your site to your Google+ account by setting up Google Authorship and Google Publisher.
Once your Google+ accounts have been created and linked, the rest is easy. Tendenci enables both Google Authorship and Publisher for the Pages, Articles and News modules.
When creating a Page, Article or News item, the interface looks the exact same.
Select either Author or Publisher (you cannot select both), then paste the URL of your Google+ page (https://plus.google.com/+yoururlhere) in the Contributor section. After you've filled out the rest of the form, click save and you're done.
To verify that you've done this correctly, you can use Google's Structured Data Testing Tool for free.