You can drill into the plastic and make clean holes right threw and use a nut and bolt or you can screw directly into the plastic. Make sure you a screw that is small enough to not go all the way threw so that you don't cut yourself or the snake on the sharp end that sticks out.......

BTW, Rich sells lights for the cages, they are kinda pricey (he does not really even mark them up because of how much they already cost, but they are the perfect light for the cage.....