I'm quite new to all the vla functions myself, so it took me a while to figure out how to use the list above.
But this works. Here is how to get the object:
(setq obj (vlax-ename->vla-object (car (entsel))))
And this to get the alignment of that object:
(vla-get-attachmentPoint obj)
And this to set the alignment of that object:
(vla-put-attachmentPoint obj 1)
Not sure how to add error handling and to check if the AttachmentPoint property actually exists in the object.