Step 1: Enabling the Joomla 2.5 cache will boost the overall performance of your web site.
Step 2: You can enable cache from your Joomla 2.5 admin area -> Site -> Global Configuration -> System.
Step 3: Select the cache option at the right side of the System page, under Cache Settings, next to Cache.There are three options:
OFF – Caching disabled – no cache support for the Joomla web site;
ON – Conservative caching – smaller system cache;
ON – Progressive caching – default, bigger system cache, the web site works faster, caches results from modules rendering, it is not suitable for very large web sites;
Next, pick the cache time for which the cached result will be stored and save the changes.