How to Hide Smush Admin Menus

function plt_hide_wp_smushit_menus() {
	//Hide the "Smush" menu.
	remove_menu_page('smush');
	//Hide the "Smush → Dashboard" menu.
	remove_submenu_page('smush', 'smush');
	//Hide the "Smush → Smush Pro" menu.
	remove_submenu_page('smush', 'smush-upgrade');
}

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

Where do I put this code?