Changing Header Image

Hi.

Ahhh man. Totally new to WordPress and after spending the last 2 hours searching reading the support forums, I still can’t figure out how to change my header image. I’m using the default WordPress Theme from Kubrick (the rounded blue one). I created my own header image with the exact dimensions as the kubrickheader.jpg image and replaced it in the proper directory but it won’t work. So… I took the actual kubrickheader.jpg image file and imported that into Photoshop and just overlayed my header image on top of the blue rounded-corners graphic and flattened the layers. I didn’t change any dimensions of the file, just the actual graphic image. I then put the file back into the proper directory (thinking it was gonna work) without changing anything in header.php. Didn’t work! What am I doing wrong? Surely, it can’t be this difficult to change the default image on the default theme, right? Whatever I do, it seems that the default blue rounded-corners graphic won’t go away; it even manages to sit on top of my personal image even if I’m able to get it to display on my blog. Grr… Can someone help please? I’ve no clue about php, css or any of this. Sorry to post here but I’m desperate!

Thanx!