With the sticker face up (clear side up) firmly rub the decal with a smooth hard object like the barrel of a ball point pen. This will make sure that all the decals stick to the clear film.
Very slowly and carefully detach the clear film from the opaque backing. The decals should adhere to the clear film. If they do not adhere to the film, do not proceed further and repeat step 1. Do not touch the decals with your fingers. Do not remove the clear film unless all the decals are on it.
Clean the destination surface thoroughly with alcohol and let dry.
Apply the clear film (with the decals) in the desired location. Firmly press the decals in place. It may help to use the waxed opaque backing to firmly rub the decal to make sure all of them stick to the destination surface.
Slowly peel back the clear film. If the decals do not adhere to the surface and stay on the clear film. Stop and repeat previous step.
After you remove the clear film. You may use the waxed side of the opaque backing to firmly rub the decals to make sure that they are properly 'set' to the surface.
They should last a long time like that. I have a similar type of decal from the same company that made these on my wife's car rear window and it is still there and looking good after 5 years.