Using Post Indexer on theme


I have installed Post Indexer Plugin on my website. I want to know how to use the index created in my theme.

So for example, i want to show recent posts from a specific category on a blog.

I have a blog called 'Test1' which has categories 'cat1', 'cat2'..

I want to show Recent posts from 'cat1' on the blog 'Test1'. Can you let me know which functions to use?