With Product theme how do I replace the site title with a logo?

Sounds like a stupid question - but it has taken me an hour of looking around and trial and error.

The nearest I came to it was under Appearance/Custom Styling under branding, where I chose the option of using a logo instead of a site title, and put in the url of my uploaded image (in the media folder) but still noting appeared.

So - how do I replace the site title with a log, please?

Regards, Paul