How does it work?
Put your articles in secret mode by checking "secret" below your article. This feature works just as well for previously published articles, as well as current ones.
Add your friends to your VIP list. They will receive an invitation to check out your secret articles. (However, this feature won't work until you have at least 1 secret article. Then you can add peeps to your VIP list.)
If you want, you can let visitors know that you have secret articles posted to your blog by changing the configuration. This will give them the opportunity to ask you to become a VIP.