How to Hide PublishPress Checklists Admin Menus

function plt_hide_publishpress_checklists_menus() {
	//Hide "Checklists".
	remove_menu_page('ppch-checklists');
	//Hide "Checklists → Checklists".
	remove_submenu_page('ppch-checklists', 'ppch-checklists');
	//Hide "Checklists → Settings".
	remove_submenu_page('ppch-checklists', 'ppch-settings');
	//Hide "Checklists → Upgrade to Pro".
	remove_submenu_page('ppch-checklists', 'ppch-checklists-menu-upgrade-link');
}

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

Where do I put this code?