This answer assumes that you've got CHDK set up successfully on your camera and can find your way around the menus. The details here are for a Powershot A570, with CHDK 'complete package', which includes the scripts you'll need (installed September 2009). From the main menu on the camera, select 'Scripting Parameters' (you can go there directly by pressing the FUNC.SET button on the camera). In passing, note that towards the bottom of the screen there is a line that says: -Default Script- Select the top item on the menu - 'Load Script from File...'