Advice for how to apply windshield banner decals

Prepare the decal to make it easier for application. In a clean, dust-free area, lay the decal face up and use a credit card/license to squeegee the surface and apply pressure so the tape sticks to the decal.
Flip the sheet over and start peeling off the paper backing layer, ensuring the decal sticks to the tape. Once you’re certain that all of the letters are stuck to the tape you can replace the backing paper to continue with the application process.
(View this video if you’re having problems removing the backing paper)

Cut away extra tape and backing paper around the curved banner.

Line up the decal on the windshield using pieces of masking tape to hold it until you’re satisfied with placement.

Use the vertical hinge method to apply the decal:

You may use a wet application method if you are concerned about the decal sticking. Before setting up the hinge method as shown above, in a clean spray bottle make a solution of ~1-2C water, 1-2 drops of plain dish soap or baby shampoo, and 1 tbsp rubbing alcohol (optional). Spray this on the windshield before applying the decal as shown in the video above, however be extra careful when squeegeeing the decal into place that you go over the entire decal to remove the water solution. Also leave the tape on for at least 30 minutes before removing to give the decal adhesive time to stick.