Don't dump all the frosting in one spot. The cake has a pretty thin layer so pour the frosting out evenly over the cake and use an offset spatula to finish spreading it out. Don't try to work frosting over too much or worry about getting it perfectly smooth. As the frosting cools it will start to set and if you spread it too much it will make it look yucky and will start to pull the cake up. A little imperfection here is going to be better than trying to mess with it too much. Add a few fall sprinkles if you don't like how the icing turned out, they'll distract from it just fine.