By setting Stop Loss and Take Profit, you can limit the amount of time you spend waiting for an outocme. Orders will be executed automatically as soon as the price reaches order level (see below). You can place Stop Loss and Take Profit at the time of making a deal by completing in the "Stop Loss" and "Take Profit" fields in the "Order" window. If Stop Loss and Take Profit levels are too close to the current price, the "Modify" button will be locked. It is necessary to shift levels from the current price and re-request for position modifying. Values in teh fields of "S/L" and "T/P" will be changed in the opened position status bar in the Terminal - Trade tab.

How to place Stop Loss and Take Profit orders in the Order window
Afterwards in order to modify Stop Loss and Take Profit levels use the context menu:

The context menu of the Trade tab of the Terminal window
Right-click on the open position or on the pending order in the "Trade" tab of the "Terminal" window then select "Modify or delete order". The "Modify order" window enables:

The Modify Order window
Fill in the "Stop Loss" and "Take Profit" fields. Selecting the red button allows you to copy this level into the "Stop Loss" field. Pressing the blue button allows you to copy this level in the "Take profit" field. The value in the "Level" field defines the difference between the order level and the current price. Once you fill in the "Stop Loss" and/or "Take profit" fields press the "Modify #position number" button.
The limits for the minimum range between the order and the current price are defined in the Contracts Specifications.
In order to delete "Stop Loss" or "Take Profit" orders, specify its level as equal to zero.
‘Stop Loss’ and "Take Profit" orders are executed in the following cases:
The order will be executed if at least one quote in the quotes flow reaches the order level. Please note, that in MetaTrader 4, charts are created using Bid prices. So:
Important: If, under abnormal market conditions, the order level falls within the price gap, Alpari (US) has the right to execute the order at the Bid or Ask price (depending on order type) of the first obtainable after the gap quote.