Spray the place of the van you want the decals on with soapy water (slightly soapy), spray the glue side of the decal with (soapy) water (better with 2 pair of hands), put the decal in place, take a plastic spatula and push out the water and air from the middle to the outsides of the decal while keeping it in the right position. Afterwards you can take a heath gun (very lowest setting) or a hair dryer to dry out the water. Should stick in place.