De-indexing my Blog

Hi, I was wondering if anyone knows how to de-index a WP Blog.
I won’t people to still be able to excess the site from the links that are out there, but need to transfer files to another new domain, has this site won’t get ranked in Google.

I know that I can stop Google from searching my site by using the ‘Discourage search engines from indexing’ settings in the reading settings tab, and I have heard that you can make the site ‘Private’ but I don’t know how to do that?

Hope someone can help…many thanks…