How to Hide MailerLite - Signup forms (official) Admin Menus

function plt_hide_official_mailerlite_sign_up_forms_menus() {
	//Hide "MailerLite".
	remove_menu_page('mailerlite_main');
	//Hide "MailerLite → Signup forms".
	remove_submenu_page('mailerlite_main', 'mailerlite_main');
	//Hide "MailerLite → Settings".
	remove_submenu_page('mailerlite_main', 'mailerlite_settings');
	//Hide "MailerLite → Status".
	remove_submenu_page('mailerlite_main', 'mailerlite_status');
}

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

Where do I put this code?