hi i iuse this camera you will find that the zebera control is in the menu as mentioned by mskvideo. how ever you if you are shooting on the run and have not got the time to set up each shot try turning on the auto iris setting (on the lens by the zoom control rocker). It a bit of a cheat but will help you out until you are more confident with the setting up you shots.
I would also recommend that you alway follow the same pattern when you set upa shoot - set the frame, check the focus, check the aperture, check the focus, check the frame, check sound, shoot the shot. all this can be achieved in less that 30 seconds when you get in to the routine.
hope it helps