Thank you for your reply.
But this is not actually what I meant. I know how to set the header image. What I meant was “Header Image Links to Site: … Check to add a link to site home page for Header Image.”, where I can set a tick mark to make sure that the header image is clickable, and when you click it, it will be forwarded to the main page, in whatever subpage or article you may have been.
In my case, I would like that link to not go to the main page, but instead it should go to some arbitrary other URL. Can I do that?