Well good news. I am going to tell you and it is easy.
So first you are going to need a rose or petal tip. I used a wilton #104. It was the biggest one I had (I kinda think bigger is better for this cake).
You are going want to hold the pastry bag pointed down with the fatter rounded side of the tip against the side of your cake and the more narrow side pointed out.
Then just go back and forth, back and forth, back and forth working your way up the side of the cake.
This process goes really quickly. Like it is the kind of cake decorating job where if you have 15 mins before you have to go out the door to take your daughter to a meeting and you have to drop the cake off at the neighborhood block party on the way and your 3 year old just came inside to inform you he peed his pants and your baby comes in covered in blue cake batter so you have to give both of them a bath and your husband calls to tell you that I-15 is a parking lot and he is running late and you still need to brush though your daughter's hair because they are going to take her picture at the meeting and your are not dressed yet, you will still have time to frost this cake real quick.
For the top it is basically the same thing, only you just go back and forth across the top getting smaller as you go in. I did one 'ruffled triangle' for every two rows on the side of the cake.