You'll need to use a UNIX terminal that supports SSH to change your password. This functionality is built in to Mac OS X, Linux, and UNIX systems; Windows users will have to download an SSH client, however. UCSD does have a Windows SSH client available for download, see below for detailed instructions.
Using SSH, login to physics-shell.ucsd.edu and enter the command passwd. For security reasons, passwords need to meet the following requirements:
Instructions on how to change your password can be found below: