Hi Joanne,
Perhaps you are running an older version where this feature is not available.
In newer systems (the example below is on a NW 7.31), you can see the 'Container Properties' section.
Even if you do not have these options in your system, you can manually create a new TransparentContainer UI element and create the Form from there.
Also, the Section Header can be manually added to the container.
Regards,
Felipe