Don't see how to make a private offer. I click on make offer but don't see where to send it private. please help. Thanks Dave

The option to make an offer Private is on the offer review page. First enter your offer including shipping, insurance or other details and click Submit. The review page that comes up next will give you the option to make the offer Private, then click Submit a second time.

If I did not see that how do I update an offer that is shown but I do not want it shown?

You cannot change an existing offer. Your only option is to withdraw the offer, then submit a new one with the private option selected.