How to Hide MailPoet 2 Admin Menus

function plt_hide_wysija_newsletters_menus() {
	//Hide "MailPoet 1".
	remove_menu_page('wysija_campaigns');
	//Hide "MailPoet 1 → Newsletters".
	remove_submenu_page('wysija_campaigns', 'wysija_campaigns');
	//Hide "MailPoet 1 → Subscribers".
	remove_submenu_page('wysija_campaigns', 'wysija_subscribers');
	//Hide "MailPoet 1 → Settings".
	remove_submenu_page('wysija_campaigns', 'wysija_config');
	//Hide "MailPoet 1 → Premium".
	remove_submenu_page('wysija_campaigns', 'wysija_premium');
	//Hide "MailPoet 1 → Try MailPoet 3".
	remove_submenu_page('wysija_campaigns', 'wysija_mp3');
}

add_action('admin_menu', 'plt_hide_wysija_newsletters_menus', 104);

Where do I put this code?