Creating an account and keys
A new user account can be created on Ubuntu with the command
[name@server ~]$ sudo adduser --disabled-password USERNAME
To be able to connect, the new user will need to have a key pair, see generating SSH keys in windows or creating a key pair in Linux or Mac depending on the operating system they will be connecting from. Then their public key must be added to
/home/USERNAME/.ssh/authorized_keys on the VM, ensuring permissions and ownership are correct as described in steps 2 and 3 of connecting using a key pair.