I usually just use some all-pupose wax, but this is going to be the wax you ride on for the first day or so so whatever temp you think it'll be for opening day would be best, but you can use whatever wax you want and then if its the wrong temp just scrape and re-wax before skiing.
To set the DIN lower, look at your binding on the front of your toe piece is usually a large looking "screw", just use a phillips head screw driver and "unscrew" it until the line in the DIN window is at the bottom, then on the heel-piece, depending on the binding it'll either be on the very back or on the release "lever", it's usually near the DIN window on the heel, once you find it just like before "unscrew" it until the line gets to the bottom number on in the window.