1. Remove the carbonating bottle before installing or replacing the cylinder if it is filled with water. Remove the drip tray grid and then carefully lay the soda maker down on its side. 2. Remove the seal and the cap from the CO2 cylinder. Carefully insert the cylinder through the hole at the bottom. Don't drop the cylinder into the hole. When you feel that it has reached the bottom, begin screwing the cylinder clockwise until it is fastened. Don't screw too hard since this might break the threads holding the gas cylinder in place.