First off, set your cool cake on a cookie rack over a flexible cutting board. 

This will help catch leftover icing that you can scoop up and re-use if needed. 

Next, microwave your frosting for two 15 second bursts- it should be completely melted but not hot. 

Let it sit for a minute or two to cool a bit (you want it still liquid- just no warmth). 

Then, in a circular motion, pour over your cake. Once you have used about 1/4 the can of icing and it looks pretty covered, let it sit and firm up for about 10 minutes. 

Microwave the icing again, for 15 seconds. 

Repeat the icing step to get a thicker, more even layer. 

Repeat once more if needed after cool. 

Once cake has set, slide it off cooling rack and onto clean cake plate. 

Decorate with sprinkles, fondant shapes, etc.

Enjoy!!