By default the options regarding the site logo and name are placed under the Global Settings of the Appearance Menu. However, in order to modify those settings while using the CERN theme, you have to change them in the Appearance settings of the theme.

More analytically, if you navigate to /admin/appearance/settings/cernclean and scroll to the bottom of the page, you will mention a group of settings called Display Site Settings. 

1. Show Site name: Whether or not you want the site name to be rendered
2. Show Site slogan: Whether or not you want the site slogan to be rendered
3. Show Search link on Main menu: Whether or not you want the search link on main menu
4. Show Dark LOGO on footer: Whether or not you want a dark logo on footer (by default it’s light). If you chose a light-colored background on your footer, then we suggest this option to be checked so that the logo will be visible.
5. Upload logo: Option to upload a custom logo.

Note: If you apply a logo then the logo will be rendered automatically.