Make sure there is no wax on the lens. You can wet the back of the vinyl with a few drops of dish soap in a cup of water. This allows you to slide the vinyl around into the right position. Once you have found that position, use your fingers to push out the soapy water. Allow to dry. LOW heat can be used to dry out the vinyl quicker.
NOTE: Items printed in clear material may appear foggy after initial install. They can require days to fully dry and become clear again.