How can I make Google+ private instead of pubic?
Privacy Settings of Google + are found at: https://plus.google.com/settings/privacy
If Google Plus is asking about anything pubic, I'd be extremely careful.
Anyway, most of G+'s settings are found at
Go there and you can change who can comment on your posts and view your stuff by default. Google +, though, is all about Circles. If you don't have anyone in your Circles, nobody can see anything that you post, so you don't need to worry to much about that.