Hi,
It is great to see you in the community. Hopefully, you will find answers for your problem. I suggest you check Dynamo Forum Guidelines that will help you structure your questions so that you can find answers much quicker.
Is it possible for you to share what nodes you tried until now?
Normally, if the Associated Family Parameter is set as an Instance parameter you will access it directly using Element.GetParameterByName. If it is created as a Type parameter, firstly I use Element.ElementType to look for type parameters and check the accessible parameters with Element.Parameters. Then, I use again Element.GetParameterByName.
Please let me know if you need further help!