If you need to disconnect a USB device, you could just pull it out, but that’s not the safest way to go.
The procedure you’re supposed to follow (though, not everyone does) is to click on the system tray on the lower right and look for the USB icon.

When you click on it, you get the option to eject the device.

It’s now safe to unplug your device.

Cyn, I think it’s worth mentioning this procedure requires administrator privileges. THANKS for your articles!
Cyn, do you think this might help with the Ext HD I can’t open? Great work, Trish