What does Christmas Icing mean to you? And what will it be applied to? This term is confusing to me. Do you mean Royal Iceing for decorating sugar cookies?

It depends on what you are using it for. If it's for cookies, sift some confectioners' sugar into a bowl. Or shake it through a sieve. You want to get rid of the lumps. Then very slowly and carefully add, a tiny spoonful at a time, a liquid like orange juice, or milk, or lemon juice, or even a nice liqueur and stir it well before adding any more. Add drops of liquid until you get it to a good spreading consistency. For cakes and other more elaborate desserts, you might want something a bit more complex, made with butter or cream cheese and confectioners' sugar, and flavorings. ;o)