I said "Terminal" not "command prompt"! :smileywink:
Type Terminal in Spotlight or navigate to: /Applications/Utilities/Terminal
Open a Terminal then copy and past the full command line as is and then press Enter and the prompt should return without any output. The command removes the fullScreenTitleBarShow key from the /Users/${USER}/Library/Preferences/com.vmware.fusion.plist file which is not present in a default install thus removing the setting that's hiding the Fullscreen Title Bar.
Note: There are other way to resolve the issue, by selectively editing the .plist file (if you know what you're doing) or with the Virtual Machine Library open you should be able to toggle between the Virtual Machine window and the Virtual Machine Library window and then toggle the state of the Fullscreen Title Bar.