Check to ensure that you have the correct piece and that it fits.
Warm up each piece. You can either put them on your vents with the heat on high (warm) or use a hair dryer.
Use alcohol pad to clean the area.
Use the 3M adhesion that they provide you. Use on the corners. Do not apply to actual product.
Peel a portion of the tape back.
Place it on and slowly peel back the tape as you align it.
Using a cloth, push down on the piece you have just installed. This will ensure that it bonds properly to the dash.