Its a bit different than Setting an Instance Parameter in a Loadable family.
If you are not familiar with how to "GET" a Type parameter in a loadable family see my previous post.
The "Family Types" node selects all the loadable family TYPES and therefore you could only "SET" that family's TYPE parameters. SO if you tried to SET an instance parameter from the Family Types Selection Node it would not work... because it only sets types....
The image will summarize this process.
Good Luck Getting and Setting Type Parameters for Loadable families.
What about System families you ask?
In my next post I will explain how to get and set parameters (both type and instance ) from a System family