Log in to create or edit your sites.
Plugins: Shockingly Simple Favicon
What it is:
The “Shockingly Simple Favicon” changes the favicon of your blog without having to edit the theme files, and put a WordPress icon in the admin interface, so you can easily spot the admin tab in your browser.
This changes are fixed so you don’t have to mess with theme code every time you change theme.
More info: https://wordpress.org/plugins/shockingly-simple-favicon/