resizeable back ground

after reading this
http://css-tricks.com/how-to-resizeable-background-image/

whlst trying to create something like this
http://zachhajjaj.com/

i am stuck and confused

can someone give me a slower idiot proof walk thru? not gonna lie, i kinda need it, lol.

the fist link says to do this

#img.source-image {
	width: 100%;
	position: absolute;
	top: 0;
	left: 0;
}

Code (markup):

but i dont know where to put it etc. i dont need the images scrolling, just a constantly resizing image

thanks DP'ers!!!!

 

U need to put those code in the CSS mate.. =)