Window tint isn't bad at all on these trucks, all of the glass is flat in at least one direction except the windshield, so tint is easy. On your back graphic, make sure you get it laminated, that way the perforations don't hold water and you'll be able to see out it in the rain (and it won't stretch the perfs when you apply it).
Like others have said, float it on with soapy water (baby shampoo is one of the popular recommendations) or if it's your first time at something like this, go buy a window tint installation kit (squegee, application liquid, spray bottle, and razor blades).
Directions below based on laminated graphic, and also applies to window tint. Directions are similar for non-laminated graphics with exception of the air-bubbles...
Wash the window with a NON-AMONIA based cleaner
Scrape the glass with a razor blade to clean off any other crap the window cleaner didn't get
Then wash it again
Soak the window with application liquid and put the graphic on the glass but leave the backing on it
Cut the graphic just oversize, the application liquid will help hold it in place while you do this
Reapply the application liquid and start taking the backing off your graphic (not all at once, start at a corner or side)
Start applying the graphic, keep the window wet as well as the back of the graphic while applying, don't worry about air bubbles yet, just keep it wet
Once you get it all mostly in place, start squegeeing the water out (and air bubbles) starting at the center and work your way out to the edges
Trim the edges to a final fit with a very sharp razor blade and you're done