To swirl icing as in picture, fit a pastry bag with a 2D Wilton tip (or a large drop petal tip). If multicolored swirl (pictured) is desired, paint thin stripes with gel food coloring on the inside of the pastry bag, from the tip to about 2-inches from the top. Stripes should be about 1½ inches apart. Spoon icing into bag and twist top to secure. Beginning at any point on the bottom of the cake, begin piping in a random back and forth and up and down swirl pattern, stopping from time to time to readjust your hand grip on the pastry bag. You want to eventually cover all of the cake. Don't worry about trying to make any pattern, it should be whimsical and random.