Using the "Private" setting means only the holder will be able to view the card.
This is done from the Business card details screen.
Procedure
1. In the Business card details screen, click on "Edit".
2. From the "Access" tab, choose "Make Cards Private", and then save.
It is also possible to make individual items of the card private, instead of the whole card.
Put a check in "Private" for the items you wish to keep private, and then save.