As Drew mentioned above, the keg will need to be hooked up to the CO2 the whole time. I find that it takes about a week of holding the keg at a constant pressure and a constant temp to get it to carbonate. If you put it into a 34F fridge today and attach it to a CO2 tank with the regulator set at 10PSI, then you should have carbonated beer next Thursday. Unless of course, you have a CO2 leak. In that case, you'll have an empty CO2 tank and flat beer. Oh, you can also leave a leaky cobra faucet attached and have a floor full of beer. For the most part, kegging has been great, but I have learned a lot of lessons the hard way over the years. That said I'll never go back to bottling.