How to Hide WP User Manager Admin Menus

function plt_hide_wp_user_manager_menus() {
	//Hide "Users → Custom Fields".
	remove_submenu_page('users.php', 'wpum-custom-fields');
	//Hide "Users → Registration Forms".
	remove_submenu_page('users.php', 'wpum-registration-forms');
	//Hide "Users → Roles".
	remove_submenu_page('users.php', 'wpum-roles');
	//Hide "Users → Emails".
	remove_submenu_page('users.php', 'wpum-emails');
	//Hide "Users → Directories".
	remove_submenu_page('users.php', 'edit.php?post_type=wpum_directory');
	//Hide "Users → Settings".
	remove_submenu_page('users.php', 'wpum-settings');
	//Hide "Users → Addons".
	remove_submenu_page('users.php', 'wpum-addons');
}

add_action('admin_menu', 'plt_hide_wp_user_manager_menus', 21);

Where do I put this code?