If you have guests on your site signing up for accounts, or guest writers writing articles for you, it’s nice to have your own logo instead of the WordPress one on your Login Screen and Admin panel.
Here’s a couple tools to help you brand these sections of your site:
As the description on the author’s site states: “The Custom Admin Branding Plugin allows you to not only re-brand the WordPress login screen, but also the admin [panel] header and footer with your own custom images”.
All of the details along with installation and usage instrutions can be found on the site (link above).
If you want to have more control and do this manually, then check out this article. It has lots of information about customizing your login screen that’s even helpful for users of the previous mentioned plugin.
Enjoy, and happy customization!