Most important of all is cleaning the surfaces destined for beautification. This has to be done very thoroughly, or the dash kit panels will eventually come off. The base surface must be free not only from dirt and grease, it has to be absolutely free from silicone! Unfortunately, many products sold as vinyl treatment products are silicone based. Therefore you must treat all surfaces as if silicone has been applied to them. Wipe the surface several times with a clean cotton cloth moistened with a wax and grease remover.
A good brand to use is Prep-ALL Wax & Grease Remover. Use masking tape to test if the surface is clean. When a piece of masking tape sticks properly to the surface and you hear a ripping sound when you pull it off, you can go on and clean the surfaces to be clad with isopropyl alcohol (which you can find in any drugstore).
Start with small and flat pieces that are easy to fit, just to get the right feel for the material and the easiest way to fit the components with the required precision