Add Wordpress Blog on Website

I have a web site for a business directory.

I want to start a blog on my site also.
Can anyone explain how can I do this?
My site URL is innobit

Either you have to convert your site to a WordPress site and add the blog or you may want to install WordPress in a sub-directory and link to your site. Review for more info:
http://codex.wordpress.org/Integrating_WordPress_with_Your_Website