>>942617Well, you need a margin account first of all.
Assuming you're using the "scottrader stream quotes" interface...
Click the buy(or sell) shortcut next to a ticker symbol. An order interface will open.
Now, click on the drop down menu under the heading "Market Side".
Select "Sell Short".
The "Symbol" field is the company you're trading. Input the quantity of shares you want to short. Select your "order type" from the drop down menu. Then press Place order. Then confirm the trade.
Remember, to cover your short you need to do all of the above, except you will need to select, "Buy to Cover" in the Market Side field.