OCEANWP

Hi I used this plugin on oceanwp to add a custom header hook on a woocommerce product category page. But it doesnt work, or rather i cannot see how to use it, once it is placed.
this is what they recommended I use in child functions.php. But I do not know how to use child theme and am terrified i will lose everything if there is an error. Can someone advise what to do?

function prefix_header_style($style) {
if ( is_product_category() ) {
$style = ‘custom’;
}
return $style;
}
add_filter(‘oceanwp_header_style’,’prefix_header_style’);