with the wet option lining up is easy as you have heaps of time. I firstly sized up the decal on the area without removing the backing cove to give me an idea or "game plan".

Then squiggy out all the excess "windex in my case" from centre to edges. Don't squiggy too much as you may squiggy out some of the adhesive as well. Then let dry and trim edges with a straight edge and sharp blade. Don't trim too close to edges, leave a small gap