add code to function.php

Hi, I'm still new to element and to php in general. My question is can I add a code to functions.php using element?

I just want to add extra sitemap support for jetpack plugin and the plugin needs to read the following code from functions.php first:

function jeherve_add_cpt_sitemaps( $post_types ) {
    $post_types[] = 'your_post_type';
    return $post_types;
}
add_filter( 'jetpack_sitemap_post_types', 'jeherve_add_cpt_sitemaps' );