To shoot calibration shots you need to point the telescope to the zenith and place the panel on the edge of the tube or hood, having previously connected 12V power supply to the controller. Then it is necessary to select camera exposure and illuminator brightness, achieving correct filling of the histogram of the calibration frame.
When choosing a Flatster line of flatfield panels, make sure that the illuminator's light diameter completely covers the entrance aperture of your telescope at the edge of the tube or hood.