Short position is selling currency borrowed from broker, with intent on buying it back later at a lower price.
Let's consider an example - a falling market. This has a potential to make profit to a trader. This is called a short position.
1) Enter the amount of currency to sell.
2) Chose margin. In short position loan amount is the full position amount, margin will let you choose how much money to use as insurance.
3) Leave the Stop loss price as is or modify it. You are able to decrease it to lower your risks, or increase it to allow for greater market fluctuations (but a higher risk to you).
4) Open your position. Detailed position data will be displayed.
5) Confirm and place your position. If the market moves while viewing the details, the position will not be opened, and new details will be offered that reflect current best offer. On a busy market this can be a little frustrating, so you can flag this feature off and open a position with best current conditions provided by the exchange.
6) Track your position. Just as with long position, use unrealized P/L column to track the position health. P/L will show negative values if the market does not favor your position at the moment, so you may close it manually at any time to stop potential loss, if you so desire. Positive P/L values mean that your position is favored by the market, and closing it at profitable value can be beneficial to you.
7) Close your position. The currency needed to repay the debt is bought and given back. You get the rest of the money (provided the position was profitable) as well as the amount reserved as insurance initially. If your position is not profitable, some of the reserved insurance will be used to repay the broker.