How to set a custom author

I have a site admin who writes articles and all his articles are attributed to him.

He also has guest contributors though, who send him posts to add to the site.

How can I set a custom author to override the admins name on these guest posts so that it has the name of the guest writer, instead of the admin? As we don’t want to create a new user for every single guest writer.

Thanks

I’ve got this sorted now. I used a plugin https://wordpress.org/plugins/guest-author/