With the Free Plan you can display up to 60 photos in your widget. The Pro Plan allows you to display more than 60 photos by adding pagination controls to the bottom of your widget.
To set this up, visit your dashboard and add a new Pro widget, making sure to select the Pagination Controls option. Click Preview and you will see Previous and Next controls added to the bottom of the widget.
You might need to upgrade if you are not already a pro widget subscriber.