==>Apple Menu ==>Control Panels ==> Appletalk ==> Ethernet (instead of Printer)
You will see a "triangle" to right of box with "Printer" or "Ethernet" in it, listing the port that Appletalk connection is currently set to go through. Click and pull down menu to select "Ethernet" if it is not yet selected.
==> Macintosh HD (or Disk drive icon name) ==> folder1 ==> subfolder ...==> folder_to_be_shared (click once to select) ==> File ==> Sharing ==> ....
To "unshare" a folder, follow the above proceedure to remove the sharing of that folder. It is also possible to go to the "File Sharing" control panel and STOP file sharing.