Press "Add Listing." Then after it says your site has been added press "Publish" below:
Publish

Then Go To Directory to see if your listing posted yet (it can take an hour or two to post).

If you happen to get an error Go Here for a back up.

This directory is provided to insure that your site is crawled, listed and maintained by search engines. Some search engines will drop listings for sites that don't have at least 1 external link.

For tips on optimizing your site for search engines Go Here.