Put your frosting in a piping bag, with your selected nozzle in the end. Make sure you hold the bag upright. Be sure to start decorating on the outside of your cake, working in all the time.
Squeeze at the top of the bag. It is very important to keep a nice, even pressure when decorating your cakes!
When you have finished a certain part of your icing, stop squeezing, and lift the bag away to avoid making a mess.