Assign Parameter to Material Parameter in Family

Hello everyone,

i want to assign an instance parameter to the material parameter of a family - so that i have access to the material in Revit.
You see the usual workflow in this video:

How do i even access the material? Do i access the material of the family correctly?

Since the material is None, i get the yellow error message

Then also: when i get the material how can i change it or how can i set an instance parameter for it?

Video is here:

Or is there any nodes/ packages that can do that?