You go to the directory above where you find your USB drive and open the context menu (three lines on the OSMC remote or c key on a keyboard). There you’ll find the option to safely remove the drive.
There’s no need to suspend or power down the Vero V. It’s designed as a low power always-on device. But if you’d still like to send it into suspend mode with a button press, @darwindesign will know how to do this.