I got it to work. Try this:
Open style.css and find line about 856:
#newswire-banner {
width: 468px;
max-height: 60px;
Change it so it fit your banner size, ie. like mine:
#newswire-banner {
width: 300px;
max-height: 130px;
Open banner-header.php and add the following in the top of the code:
<img src="https://www.yoursite.com/wp-content/uploads/righttop.jpg" width="300" height="130" align="right">
And ofcouse upload your banner as https://www.yoursite.com/wp-content/uploads/righttop.jpg
Always make a copy of your files before editing them, so you can go back if something messes up.
Hope this helps you a bit on the say.