Clean the surface with a non-abrasive cleaner. Soap and water should be fine ;) Dry the surface and make sure that there is no soap left on it. Optional you can spray a fine mist of water on the surface. This will allow you to reposition the graphic a bit if needed.
Holy shit what's that ! It's mister Bubble :P You can try to remove them with an object like a credit card.
There he goes. If this doesn't work then just let it so for a few days, normally it will shrink a little. You can also try poking them, but this is not recommended because mostly it will look quite ugly..