Access to all linux-based HPC resources is via secure shell ('ssh'). In addition, if you are connecting from off-campus, you will need to connect to the VPN first. There are a variety of ssh clients available for most operating systems.
On Linux systems, you should be able to open a terminal and ssh directly to the machine of choice. So, to connect to the gibbs HPCC, you could:
joeuser@mycomputer:~$ ssh email@example.com firstname.lastname@example.org's password: Last login: Mon Oct 28 13:55:59 2013 from mycomputer.umb.edu
If you want to run X11 (GUI) applications remotely, you should include the -X command line option to ssh:
joeuser@mycomputer:~$ ssh -X email@example.com firstname.lastname@example.org's password: Last login: Mon Oct 28 13:55:59 2013 from mycomputer.umb.edu
Mac OS X
On OS X, the procedure is similar to that for linux. First open a terminal window, then use the command line to ssh to the remote machine as above.
On a windows machine, we recommend that users consider installing Cygwin/X, particularly if you plan to use X11 applications on the remote system. Cygwin/X emulates a unix environment on your windows machine. Once that is installed, you can open a terminal window and ssh as above. Another popular client is PuTTy.