How to Hide the "E-Signature" Admin Menu

function plt_hide_ninja_signature_contract_forms_add_on_menus() {
	//Hide the "E-Signature" menu.
	remove_menu_page('esign-ninjaforms-about');
}

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

Where do I put this code?