I would suggest you start by reading the
Windows Home Server section of the Microsoft web site, including the various documents available there and on subpages. You'll have a much better idea of what you can, and can't, do with the product.
For your specific question: no, Windows Home Server doesn't allow you to share an arbitrary disk or folder. You create and manage shares through a purpose-built management console, then Windows Home Server manages all your disks and shares for you.
I'm not on the WHS team, I just post a lot. :)