how to ad a function in a hueman child theme

Hi,
I have 3 hueman child theme (I have a multisite with two subfolders) with a minimal customization in the style page and in header.php.
I read: https://docs.presscustomizr.com/article/239-using-a-child-theme-with-hueman
Still not clear how to add the function.

i want to add a function, that I don’t think it overrides a function of the parent theme.

1) The function I want to add:

add_action( 'wp_enqueue_scripts', 'custom_contact_script_conditional_loading' );

function custom_contact_script_conditional_loading(){
   //  Edit page IDs here
   if(! is_page(2383) )    
   {		
      wp_dequeue_script('contact-form-7'); // Dequeue JS Script file.
      wp_dequeue_style('contact-form-7');  // Dequeue CSS file. 
   }
}

Disables the load of contact form 7 in each page, and enable it in the page with chosen ID

2) The question is:
Where to add this function? wp-content/themes/hueman-child-theme/function.php?

Needs some extra code to be added?
Thanks in advance

The page I need help with: [log in to see the link]