First of all, make sure that the Header Top Bar is enabled. How to enable the Header Top Bar?
From your WordPress Dashboard, go to the Appearance > Customize > Header Options > Header Top Bar section.
Underneath the Left Content/Right Content options, you can use the dropdown menu to select one from the Text/HTML.
If you choose Text/HTML in the Left Content/Right Content options, you can insert the content in the editor below. You can also switch between a Visual Editor and a Text Editor using the tabs labeled Visual and Text.
If you want to directly add a media file, you can do so from here by clicking on Add Media.
How to Add Content on the Header Top Bar?