Your icing is definitely too think. The wilton recipe as it is written is a stiff icing. for each cup of icing you need to add 2 tsp of water to go from stiff to thin and thin is what you need for icing a cake. When you get it all mixed up and stand your spatula in it, if it is thin it should easily fall over if you wiggle your bowl. If it is thick it will remain standing. Hope that helps.