I have attached the form contents preset that I use.
First I click on the Insert CSS Form button. Then I select "Firth Web Works" from the "Choose a form" drop down and then for "Choose a design" I leave it at the default "New From Blank".
The form is added to the page.
Next I click on the form and click on the "Edit Design" button in the properties panel.
But from here it's not always the same. Sometimes it will save it OK for a number of edits, but then, it attempts to copy my entire C drive to the CSSFormBuilder/FD_XXXXX_Default folder and Dreamweaver stops responding.