Change topbar content
Go to Appearance → Widgets, on the right side of the screen you will see the “Topbar” panel. You can add widgets from the left side of the screen to these panels.
Change topbar colors
To change the colors of the topbar (background color, text & link color) please navigate to Appearance → Customize → Topbar there you can find the color settings.
To hide the topbar please navigate to Appearance → Customize → Topbar and change the “Display topbar” field.