Tips on Customizing Groups

How to Hide Groups Admin Menus

function plt_hide_groups_menus() {
	//Hide "Groups".
	remove_menu_page('groups-admin');
	//Hide "Groups → Groups".
	remove_submenu_page('groups-admin', 'groups-admin');
	//Hide "Groups → Capabilities".
	remove_submenu_page('groups-admin', 'groups-admin-capabilities');
	//Hide "Groups → Options".
	remove_submenu_page('groups-admin', 'groups-admin-options');
	//Hide "Groups → Add-Ons".
	remove_submenu_page('groups-admin', 'groups-admin-add-ons');
}

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

Where do I put this code?

How to Hide the "Groups" Meta Box

function plt_hide_groups_metaboxes() {
	$screen = get_current_screen();
	if ( !$screen ) {
		return;
	}

	//Hide the "Groups" meta box.
	remove_meta_box('groups-permissions', $screen->id, 'side');
}

add_action('add_meta_boxes', 'plt_hide_groups_metaboxes', 20);