Kate Hemmings on The Crafts Channel shows that covering a cake isn't as tricky as you may think.
You will need a type of icing that rolls out, such as fondant icing. Ideally, you will want to have fondant icing with glycerine, and so the Pettinice brand is excellent in this case. If you use this icing, you will not encounter problems with cracking of the icing when you try to shape it over the cake.
First, you will want to create a solution of icing sugar (or powdered sugar) and water in a separate small container. You should also have a brush to apply this solution onto the icing.
Then, roll out the icing over your rolling pin. Apply some of your sugar/water solution to the icing as you are rolling your icing out- this adds flavor and improves the texture.
Just pull the rolled layer of icing over the cake, and gently press the sides of the icing against the cake to flatten the icing.
Cut off excess icing, but leave enough extra to cover the plate.
You may shape the excess icing with a clean stamp or tool of your choice. Kate suggests using a shell tool.
Then, using your ironing tool, smooth out all the sides of the cake, including the top.
For decoration, Kate suggests adding a ribbon. To do this, she adds the sugar/water solution to the areas that the ribbon will be placed over, and then she ties the ribbon over. She adds a selection of daffodil leaves to the top of the cake, though you may decorate your cake with anything that you choose.