command crea forma..

[ximo]

Bye to all,
I'm desperate, it's just that I've been using revit and I've been modeling a 3d with a very irregular cover and I wanted to use the mass, but at the time when I have to create the shape I don't find the appropriate command "create form", would you know how to help me? ? ?
Thank you.

 

[Tristan]

select 2d geometries and you will see that it appears in the ribbon...