RBVM Ssh
First of all, you will need to install an ssh server on your VM before you can ssh to it. You will probably need to do this with a VNC Viewer. When your in your VM, you can install OpenSSH with:
apt-get install openssh-server
Access from other Redbrick servers
Note your VM's IP address from the VM Management page. To login simply ssh to that IP address, with your VM user/pass (not your Redbrick login details).
ssh username@IP_ADDRESS
Access from an external machine
You will need to setup a tunnel to get to your VM, if you're accessing from outside Redbrick. To do this, type:
ssh -L 1337:YOUR_VM_IP_ADDRESS:22 username@login.redbrick.dcu.ie
This binds port 1337 on your own computer to your VM (on port 22, the ssh service). So to connect to your VM:
ssh 127.0.0.1 -p 1337