Hi Cyee, if you shift the gearlever to the left from D it goes into DS mode i.e. Sport Mode for more performance but still automatic - the dash will display DS. Now while in DS mode, if you flick the gearlever up or down you'll be in Manual mode (the dash will show M and the gear you're in e.g. 2nd gear will show M2) - so now you change gears by yourself - flick up/push to change down, flick down/pull to change up a gear.
Hope that clears it up for you. It will take getting some used to. Also note that when slowing down in Manual mode the gearbox will automatically shift down a gear for you.