Okay dude, as you can probably guess by the responses, filling your bottle is something that should only be attempted once you have been shown how to do it safely and know exactly what you're doing. You're dealing with very high pressures which can be very dangerous if not handled correctly. You can tell what type of bottle you have in several ways, but the easiest is to look and see if there's a pressure gauge/fill nipple on the side. No? Then it's probably CO2. Never fill a bottle with anything it's not intended for! Take it to your local site and have them fill it. Ask them if they can show/explain how to do this, and then after watching a few times and listening very carefully you may attempt to do it yourself, unless you're under the age of 16, in which case I recommend you have an adult perform the task for you. That's my advice anyway.
