After creating an account you can change that account's password by logging in or by writing command su - <username> in the root terminal then entering.

Once that's done enter command passwd. If you accessed from root account then you can just type your new password and repeat if but if you logged in as the user itself and if that user doesn't have root privilege you need to confirm your current password (if any) to change it.

As for changing the username, it is possible, so please read this.

From VMware you can only change the VM name, system resources and other settings only.

P.S. : One more thing, you seem to be new to this and so I assume you might be a bit overwhelmed but don't worry, it's pretty easy and logical. And, please try searching and reading about these problems first on https://askubuntu.com/ or https://stackoverflow.com/ or some forums like those as most of your questions have already been answered there. It will be much better if you'd try to find answers by yourself first. :)