Corn sugar is a carbonating source applied after the beer has comleted fermenting. It can either be added to the bottling bucket, or directly to the bottles before capping the beer. The only problem with adding it to bucket is that you must make sure that the bucket is completely sealed during the carbonation process. This means that you can't use the airlock. I personally learned this the hard way on my first batch. The majority of the carbonation will occur within the first 48 hours, but don't get anxious and start drinking qiute yet. The beer will not have aged properlly and may contain some off-flavors that will disappear with time.
Other sugar sources can be used in place of corn sugar, but it is necessary to know exactly how much sugar this new source has. Typically used sugar sources include; brown sugar, cane sugar, honey, malt, and molasses. These sugars may also add some interesting flavors to the beers.