Sharing files to the BB does not in itself make the BB 'visible' to the PC.

In order for the BB to work with any other LAN units at all, or with the Internet, you need to use the submenu "Settings" / "Network" / "Network", to set up the basic network parameters. This you probably have done correctly already, or the BB would complain about a missing connection each time you start it.

In order for the BB to 'see' shares of the PC, you also need to use the submenu "Settings" / "Network" / "SMB client" to configure the BB to use a specific PC user account and workgroup, in making its SMB accesses to the PC.

And in order for the PC to 'see' shares of the BB USB drives, you need to use the submenu "Settings" / "Network" / "Servers" to activate Windows filesharing from the BB USB drives.