To be able to share photos with others, then you should have to register on the Portal: http://pinterest.com
To activate the service in the store, you must:
1 Go to the menu CONFIGURATIONS > LAYOUT > ACTIVE THEME
2 Select a bookmark "Product details" and select "Pin it" to Yes
From the moment you select this option, you will see the "Pin it" image next to your product, and the button will be available.