Programmatically adding fields to node submission form
Add something like this to your hook_form_alter().

$form['#submit'] += array('mymodule_another_submit_handler');


Create that function and save your values from $form_state['values'].

function mymodule_another_submit_handler(&amp;$form, &amp;$form_state) {}


Where are they supposed to go? You might try to fire the submit handler of the other form so you wouldn't have to write so much code.