Placing a stop loss on a position can be done in many ways. You can place it by clicking and dragging the position on the chart itself which will visually show you the take profit being placed. Another way is to press the small pencil icon on the “Take Profit” in the “Open Positions” section.
To place a stop loss prior to opening a trade, press the “+ New Order” button next to your symbol, press on “Take Profit” and write your level, and then proceed to enter a trade. Also note a great feature, that by doing this you are able to select the take profit level and all trades open by one click trading will open with that same Take Profit level which will save you a lot of time of having to edit them all one by one after opening.