The operation can’t be completed because you don’t have the necessary permission.

hello ! since a 2 days i am trying to install bootcamp but i have LOT OF EL CAPİTAN errors my mac is became idiot with such an idiot el capitan.

My first question : why bootcamp dont see my WİN 7 DVD. i got EMPTY DİSC message

Then : i can not see option to install Win 7 with USB.

also i am trying to add that option with this way : contents/info.plist change this info.plist... as you know. But again i got : The operation can’t be completed because you don’t have the necessary permission. message !

really what can i do ! i want to trash my İmac 21.5' after el capitan ... PLS HELP