How do I change header banner from 480×60 to 720×90

Unless you provide a link to a page demonstrating the problem, no one will be able to offer much in the way of assistance.

Thank you esmi. This is the link https://www.sojblog.com. I already have a 480×60 size banner there but I want to increase it to 720×90 banner and maybe reduce the size blog logo.

I can’t see any banner in your header…

What I mean by banner is the advertisement beside the blog logo.

What I want to do exactly is this:

I have adsense ad in the header but the size the header can take is 480x60px. I want to change this size to 720x90px. What do I need to do?

You would need to start by reducing the width of your site’s title in style.css:

#image-logo a {
    height: 60px;
    overflow: hidden;
    text-indent: -5555em;
    width: 300px;
}

Okay. Thank you. Lemme check that.

I have tried it but it does not work. I only affected the blog title but the left side which houses the advert does not increase. I think I have to increase this too. Pls how?

Try using Firefox with the Firebug add-on for this kind of work.
https://getfirebug.com/