virtualisedcityadmin on "iFrame background"

WordPress newbie here, I'm trying to create a background for my website using an iFrame...
I have put a z-index on everything to try push the iFrame to the back but it hasnt worked for me
below is my coding

After some Googling ( https://www.google.com/search?q=iframe+z-index&ie=utf-8&oe=utf-8 ), apparently the items with Z-Index need to have a relative, absolute, or fixed position.

yes after googling myself I found the same thing and applied it to my CSS but still didn't do it for me..

https://jsfiddle.net/75gL60s7/1/#&togetherjs=j852w8uAsk