Click the "All Tabs" link
Click the Configuration Center tab
Click the Enable button under Enable Testimonials for Facebook
A new browser tab/window opens to add the Testimonials tab to your Facebook Page. Select your Facebook Page and click Add Page Tab.
Go to your Facebook Page
Click "See more" to see the Testimonials tab
Click the Testimonials tab
Enter your Salesforce.com Organization Id
The Testimonials tab should now load, if you've marked your testimonials as "Share Online".