ISSUE SUMMARY:
In the attached image - I would like to get rid of the space between the image and the top of the red menu.
How can I do that?

Hi Ofer,

On your CSS file you can add this code :

header#t3-header {
    padding-bottom: 0px !Important;
}

this might sound stupid... how do I get to the file? :)

via FTP file, download the file first, edit it, and upload it.. :)

My question is which file is it. Where do I find it when browsing with the FTP tool?

Forget it, I already applied it via socialize custom code

Please don't do that.
1. I wanted to learn, so I don not open another ticket in the future.
2. You did it in the wrong environment. I did not want to do that in our Production environment, but in out test environment.
But... your image was enough for me to figure out where that was, so I copied it into our test environment as well.

Thanks!!