andij731 on "How to insert images into corners of the site?"

I am a newbie to wordpress and know very little about coding etc but have been designing my site through trial and error and from searching this forum for advice. However there are a couple of things I am struggling to do which I could do with some help with.

I am trying to add some corner swirls into each of the far corners of the site (I have 4 separate png images that have been designed for this).

http://www.beauty-deals.co.uk/wp-content/uploads/2013/08/swirl4.png

I have tried a couple of things, (with links to the images I have uploaded to media), but they didn't really work

ie

#upper_left {
width: 125px; height: 125px;
position: absolute;
top: 0; left: 0;
background-image: url("http://www.beauty-deals.co.uk/wp-content/uploads/2013/08/swirl2.png");
background-repeat: no-repeat;
}

#upper_right {
width: 125px; height: 125px;
position: absolute;
top: 0;
right: 0%;
background-image: url("http://www.beauty-deals.co.uk/wp-content/uploads/2013/08/swirl2.png");
background-repeat: no-repeat;
}

#lower_left {
width: 125px; height: 125px;
position: absolute;
bottom: 0%; left: 0;
background-image: url("http://www.beauty-deals.co.uk/wp-content/uploads/2013/08/swirl4.png");
background-repeat: no-repeat;
}

#lower_right {
width: 125px; height: 125px;
bottom: 0%;
right: 0%;
position: absolute;
background-image: url("http://www.beauty-deals.co.uk/wp-content/uploads/2013/08/swirl3.png");
background-repeat: no-repeat;

Here' s my sites url http://www.beauty-deals.co.uk/

Any suggestions as to what codes I need to do this? As I'm a beginner to wordpress can you please tell me exactly where on the CSS I need to put the coding. I don't really understand about child themes etc and I have just been going to editor and changing the coding there (which I'm sure is probably not the right thing to do!!).

I have tried the above coding under

}
body{

and under

}
#main {

Any advice would be very much appreciated.

I am also trying to put a border round the main white contents box of the site so that it appears whatever page you are on. I have managed to do this for a border for the slider but can't figure it out for the main body box.

Any suggestions??

Thank you