To place an order you need to first find and select the instrument you wish to trade on, in the Market Watch.
After doing so, you can either:
Right-click on the instrument -> New Order:
Or, drag and drop the instrument in the main page, to open its chart -> right-click somewhere within the window -> Trading -> New Order:
Whichever method you use will pop up the following table where you need to fill in the specifications of how you wish to execute the trade.