Access over VNC lets you control and install your VM. Once you've set it up you can access it over ssh
You will need a VNC client on your computer to connect. On linux etc. any VNC client provided for your distro will do. On windows you'll need something like realvnc
The VNC ports are not open to the internet. You can access them only by tunnelling over ssh to minerva. Instructions for this are shown along with the VNC password when you turn on a VM.
These are randomly generated each time you start your VM. The passwords are not stored on the system, so, if you lose the password you'll need to restart the VM to connect over VNC