SSH
General
Secure Shell (ssh) is a commandline-tool for logging into a different computer over some network (e.g. the internet) and for executing commands on that machine, as if one would be sitting there instead of the own computer.
Access
OpenSSH is the standard ssh client on Linux and MAC and it is freely available for everyone. On Windows you can use Putty or the Gitbash (coming with ssh) which is also free.
Manuel
Text more remote access to an HPC system is typically available over the encrypted secure shell protocol. Logging in with OpenSSH on a Linux Cluster is done with:
$ ssh -l <login> <cluster>
Here login is your user name and cluster is one of the frontend nodes of the system. A list of frontend nodes is provided as part of the side specific information.
If you need to start graphical applications you need to enable X11 forwarding/X11 tunneling by your ssh client. For OpenSSH this is done by giving it the "-X" command line option:
$ ssh -X -l <login> <cluster>