Clean the area on your ski where the sticker will be applied well with methylated spirits.
Spray ‘spray and wipe’ or ‘windex’ over the area where you will be applying the sticker.
Take the backing off the sticker and place the sticker on top of the sprayed area – you can then move the sticker around to ensure it is in the desired location.
Use a cloth/credit card or similar to push away the excess spray and wipe / windex from under the sticker.