Public or private makes no difference if you use the VirtualBox shared folders. The prerequisites are below (taken from the section I sent you)
(1) Guest additions need to be installed (in the guest)
(2) you map (define) the share in the shared folder section of the guest. (guest shut down is the easiest)
At this point you start the guest and either look in the network section and vboxsrv for you shared folder or you can map it with the net use command.
If you want to do a standard network share (not shared folders) you would need to change the network from NAT to Bridged or Host-Only so they networks are in the same network segment.
Note: when naming the shared folder do not use anything elaborate. Just something simple like share. No special characters or spaces.