1. The first step is to determine the height and circumference of your cake, so that you cut the chocolate to the appropriate size. Using a ruler, measure the height of the cake. You can either cut your chocolate to the exact height of the cake, or make the chocolate slightly taller if you want to make a barrier and cover the top of the cake with fresh fruit, or a layer of poured ganache or mousse.
2.After you have determined the height, measure the circumference around the cake. The easiest way to do this is to use yarn or kitchen twine and wrap it loosely around the base of the cake. After you have your measurement, add additional inch or so to the total to ensure that the chocolate will wrap all the way around without any gaps.