How to replace tagline with image?

You need to create child theme (How to create Child Theme)

And replace the tagline code with your logo / image in header.php

Any easy way to modified directly on current theme ?
Could you please tell more detail how to replace the tagline code

Find this code on your theme header.php file

bloginfo('description')

and replace your image code

<img src="IMAGE URL" alt="logo" />

But its not recommended way. May be you loose your code when you update your theme