PHP code for home page

Hello,

I want to use below code for home page to show only blog category posts:

<?php
function generate_home_category( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'category_name', 'blog' );
    }
}
add_action( 'pre_get_posts', 'generate_home_category' );
?>

How do I do that?

Regards