You'll just need a clean surface to apply your sticker onto.
Simply use paper towel and a good cleaner like Windex or alcohol to clean your surface with. Line it up first to make sure it fits in your desired space.
Then peel the backing off.
After the backing is off, carefully place it where you want it, then use a squeegee (a credit card will work for this) and run over the sticker with added pressure for it to stick to your surface. Start in the middle of the decal and work out in all angles. The adhesive is pressure sensitive and needs to be burnished on.
Then begin to peel the application tape off the sticker. Start from one end and peel away from the surface at 180 degrees (pulling it back over itself).
Now just go over it with your hand and smooth down the sticker and you now have a nice looking vinyl graphic!