How to Hide Seonix SEO Admin Menus

function plt_hide_seonix_menus() {
	//Hide the "Seonix" menu.
	remove_menu_page('seonix');
	//Hide the "Seonix → Problems" menu.
	remove_submenu_page('seonix', 'seonix');
	//Hide the "Seonix → Settings" menu.
	remove_submenu_page('seonix', 'seonix-settings');
}

add_action('admin_menu', 'plt_hide_seonix_menus', 11);

Where do I put this code?