Charging Your Soda Siphon
To charge your soda siphon, pull out the inner workings of the soda siphon (there is a plastic sleeve that fits in the top, and a tube that fits inside of the sleeve that extends to the bottom of the bottle). Then fill the soda siphon most of the way with water of your choosing. Leave about 2 inches of headroom in the bottle. Now put the plastic sleeve and tube back in place, and screw the top onto the bottle tightly.
It is important to leave some room in the bottle to accept the CO2 charge, so do not fill the bottle all the way to the top with water. When the top is screwed on securely, there should be no screw-threads visible.
Then put a CO2 cartridge into the charging sleeve. Hold the soda siphon sideways (i.e., parallel to the ground), and point the output nozzle into a sink (or at least, away from people). Now screw the charging sleeve onto the soda siphon charging valve. When you screw it all the way down, you will hear the cartridge discharge into the soda siphon.
There might be a small burst of fluid from the output nozzle if it was not closed all the way, but the pressure from the charge will cause that valve to close immediately. This is why it is important to point the nozzle away from anything when you screw in the charger.
You may unscrew the charging sleeve and dispose of the spent CO2 cartridge. If you have a 2-quart soda siphon, repeat the process with a second CO2 cartridge.
Once your soda siphon is charged, shake the soda siphon vigorously to distribute the charge throughout the water. Once your soda siphon has been shaken, it can be used immediately, however you will get better results if you allow it to sit in the refrigerator for a few hours first. This will allow the gas more time to infuse throughout the water, an it will allow the water to chill thoroughly.
To dispense soda, hold the bottle upright (or at a slight angle), and simply squeeze the handle downward. Shake the soda siphon before and after each use to keep the "fizz" in the water.
You can store your soda siphon in the refrigerator to keep the soda water cold. Always shake before using.