How to add new social account Like "Instagram" in Social Links section?

Activate child theme first. then add the below code in your child theme function.php file

add_filter('social_links_array', 'func_social_links_array');
function func_social_links_array($social_array){
    $social_array[] = 'instagram';
    return $social_array;
}

Instead of instagram you can use any other social account.