Automatically select Project Base Point

I wrote a dynamo script to automatically rotate the true-north arrow. I can’t upload the dyn-file, so see below the screenshot.
I can manually select the Project Base Point and then manually select the North-arrow family to adjust the “angle to True North”. so far so good. but how do I have it automatically select the Project Base Point and also automatically select that north-arrow family?

I played a bit with “Element Types” and “All elements of Category” nodes to select the base point, but can’t get it to work. what I want is to open a Revit project, run the script and all north arrows will automatically be correct without having to manually select base point and north arrow family.

I just started with Dynamo yesterday, so there sure is something I’m missing.