This tutorial explains how to configure your Joomla! to use Memcached.
Joomla! natively supports Memcached. This means that you just need to enable this option. In order to do this you need to edit the Joomla! PHP configuration file - configuration.php.
This file is stored inside the web root folder. You need to open the file and find the following two variables:
public $caching = '0';
public $cache_handler = 'file';
Edit them and change the code to:
public $caching = '2';
public $cache_handler = 'memcached';
public $memcached_server_host = '127.0.0.1';
public $memcached_server_port = '11211';
Note that you should replace port number 11211 with the correct port number for your hosting account. You can find more details how to find the Memcached port for your account here.
That's it - your Joomla! is now correctly configured and it uses Memcached to cache API calls, database calls and objects.
If you access the Joomla! administrative area you should be able to see the following settings under Site -> Global Configuration -> System tab: