Seems to me, Shorting works something like this:

1.  Set up a margin account.

2.  Borrow the Shares (usually in blocks of 100).

3.  Sell the Shares.

4.  Maintain 25% (or whatever is required by broker) in your margin account.

5.  Buy the Shares back when you are satisfied the downside is done.

6.  Return the Shares.

7.  Pocket the difference, less fees.