http://wiki.i2p-projekt.i2p/wiki/index.php?title=DNS_registration
You don't need to touch this to add your eepsite, you would instead register it with a registry. The private addressbook, is, private. This means it is shared with no one else and only in your router. It can be used, for example, to save a service that you operate (like a SSH or an FTP server) or a private forum that no one else should see.