Wow, you learn something new everyday!Oh dear!!!
Was just looking for pics or videos to show you what candling is but read that you shouldn't do it past about 2 weeks into the incubation period. Basically what it is, is a method by which you can check to see if a) you've got fertile eggs and b) how the embryo is developing. I used to just take a good torch out at night, pick up an egg from under the chicken and shine a light behind the egg, so I could see through the shell, into the egg.
This will explain it better:
http://chickenbreedslist.com/Egg-Candling-What-It-Is-and-How-To-Do-It-Correctly.html
And this site has a few pics:
http://www.raising-happy-chickens.com/hatching-chickens.html