Creating a div before Header

Hi,

I am looking to create a <div> to insert an external image so that it opens a container the size of the image, and avoids triggering content shift later on. I added the specs in CSS:
@media only screen and (min-width: 768px) {
.my-div-name {
min-height: 250px;
}
}

Can I use Genesis Simple Hooks, Before Header, to create ‘my-div-name’? If so, which code would do the job?

Thanks