You can place a trade using your online account:

• Click Find & Invest from the menu and search for the instrument you wish to trade.
• Then click the Buy button or Sell button. 
• Enter either the quantity of shares or cash amount you wish to buy or sell.
• Click Get Quote to get a quote for your order which is valid for 15 seconds.
• If you are happy with the price, click Place Order to confirm your trade.

Please note that you will need to get set up for international investing before you can trade US and other international shares.