i want to make site logo changer  using forms , but i dont know how to code the action

this is my form code:

$fields = [
    [
        '#type' => 'file',
        '#label' => 'Photo',
        '#help' => $upload_limit,
        'name' => 'headline_photo',
        
        
    ],
    
    
    [
        '#type' => 'text',
        'name' => 'headline_title',
        '#label' => "Headline",
        'value' => $site->headline_title,
    ],
    
  
    
    
  
];

foreach ($fields as $field) {
    echo elgg_view_field($field);
}

$footer = elgg_view_field([
    '#type' => 'submit',
    'value' => elgg_echo('save'),
]);
elgg_set_form_footer($footer);

 

 

please give me code that will save logo for my website ,

and tell me how to show it in the website , for example : $site->getLogo() or something else

my client is not programmer , so i want to make it easy for him to change the site logo if he want to change it in the future