Recently I developed a site using wordpress. I am new wordpress user, so I dont know how to add meta description for my site. Can any help me?
Download and install 'All in one SEO' plugin. You'll have to go on each page and edit the meta etc., fields.
...as a new WordPress user it might be confusing with pages and posts... make sure all your post gets meta descriptions, titles and keywords... All posts become separate "pages" with a unique URL. In the general settings for the plugin "All in One SEO", the meta description for the home URL is set... and then other pages and posts are set on the same screen as you add/edit pages and posts. Just make sure to give your descriptions some variations...
All in one SEO is the best plugin for wordpress which force the power of your site and make good result in search engine. You should apply All in one SEO in your wordpress site.
The best way for you to do that is to add an SEO WordPress plugin. Try Yoast's SEO Plugin. http://wordpress.org/extend/plugins/wordpress-seo/ Install and activate. Once active, you will find a form just below your editor (when you create/edit a post) where you can add your meta data, specific to a page. If you are using Thesis like I do, this kind of option is already built-in so I don't really need to install any plugins.