How do I do it? I have a logo ready to go, but no idea how to change the default one.
all design changes are made in the template.htm file from your theme (it's plain html)
It really depends on the theme but in this case the header image is changed in the style.css file.
Find in the style.css file and edit accordingly:
#menu {
background: url("images/menu.jpg") no-repeat;
width: 685px;
height: 125px;
float: left;
text-align: left;
}
Or just change your image name to "menu.jpg" (assuming it's a jpg file! ;)).
That's why board rules say that you need to post a link to your gallery. We need to take a look. Read up board rules, then do as suggested. It won't hurt to post a deep link to your header image as well.