You can't use shorting as "stop loss" orders - meaning if you hold a stock at $100, you can't set a "sell" (or cover) order to sell it if the stock drops in price to $95. You can't short to prevent losses in your port...only to earn profits.
EXAMPLE: You short MOVIE stock at $50, because you think it's a terrible movie, and no one will go see it. So you short it at $50, and 2 weeks later MOVIE stock drops to $45...you have made a $5 profit on your "short."
However, if MOVIE stock goes UP in price to $55, then you have "lost" $5/share when (or if) you sell it (or in this case "cover" it).
When you want to BUY a stock, you SELL it when you want to get rid of it.
When you want to SHORT a stock, you COVER it to get rid of it.
You lose money if you have a stock short and the price rises.
You earn money if you have a stock short and the price drops.