Great question. I actually just did my first 2L carbonation this evening. Because I am relatively new to soda making I picked up a 5 pound CO2 tank off of eBay (there are some great sellers on this site with great deals as well).
What I needed (Your Mileage May Vary)
1 x 2L soda bottle (old coke bottle for me)
1 x CO2 Cylinder filled
1 CO2 Regulator
4feet of braided PVC
2 hose clamp dealies
1 ball lock gas valve
1 Carbonation Cap (liquid bread)
Took a while to get everything together but less than 2minutes to have carbonated water.
Theres some good articles if you search through the soda making forum.
Originally Posted by Flyboy718
How do I carbonate with that adapter? Do I have to buy a bottle of CO2? What size and where?