Option 1: Form on same page as article (content view)
Option 2: Article selected within the form. (are there more options? hmmm...)
Option 1
Create a new field of type Text and put it in your form. Let's say the machine name is 'art_id_value'
Select [2] in your form to get access to live values.
select 'url' for Live, and in live values click 'configure', and for variable enter 'id'
You might as well set the type to 'int' (integer) for good measure
Now you will have the article's id placed in the form for reference. If you do not want to store the id, set Storage to 'none'.
Create a new field of type Afterstore and enter code that updates a db record similar to the code below:
Option 2
Create a new field of type Select - Dynamic and put it in your form. Let's say the machine name is 'art_id_value'
Create a query to get desired values.
I use the 'Query' : 'Free' option to write the query, and the example is below:
// gets results if beforerender
$fields['art_id_value']->form;
// gets results if beforestore
$config['post']['art_id_value'];
// gets results if afterstore
$config['post']['art_id_value'];