Customizing template

I use the Goran template, and I want to customize the header image. I want to make it smaller and modify the layout a bit.
My site’s url is .
I want it to look like this, to have these margins and paddings circled here, and I don’t know how to modify them, because they aren’t in style.css, and dreamweaver can’t modify them, it says “read only”.

Please help me to customize it!