The way I do it with great success is to take some Windex and spray it liberally on the fender, then I spray some more and apply the decal on the wet fender. It will give you plenty of time to adjust as needed. Then I work the fluid out with my hands. It helps to warm the decal up prior to application. Just warm it so its pliable...not melted ...Oh and prior to application use Iso Alcohol(rubbing) or denatured alcohol to clean the area prior to application of windex.
They do make decal pre application fluid, which I have used but windex works the same.