If you go to the Home Depot page you linked to, Scroll down until you find the Product Overview. To the right of thst you will find a box that says "Info & Guides". Inside that box, like on most product pages on Home Depot's website, you will find installaion instructions (pdf download).
Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space. If you insist on it facing the metal skin of your vehicle, then you need to allow at least a 1/8" air space (best provided by a layer of bubblewrap packing material). For mobile applications, I would suggest that you face the barrier towards your living space. Use an adhesive made specifically for "foamboard" (you can find it in the Paint Dept at Home Depot). Other adhesives will dissolve the foamboard. And then it falls off the wall or ceiling, usually at the worst possible time.