For a 5 gallon batch, I use 4 ounces. I think that's around 2/3 of a cup, but I do weigh it so I'm not sure.
You boil two cups of water, add the sugar, and dissolve and boil that for a minute or two. Then cool it, and pour it into your bottling bucket. Then rack the beer into your bottling bucket. It's best to have a long siphon tube to reach the bottom of the bottling bucket, so the beer doesn't splash. I put it at an angle at the side of the bottom, so it kind of curls a little, and then the beer "swirls" to mix at the bottom as it transfers into the bottling bucket. Then I use the bottling wand and fill each bottle.