To start the vnc server, ssh to math.utexas.edu and run the command
Then use a VNC client on your computer to connect to the server. Part of the output of the vncserver command will say the hostname and the display number. It will look like this:
New 'X' desktop is lab22:1
In this case, lab22 is the hostname and 1 is the display number. You will need to append ".ma.utexas.edu" to the hostname when you enter it in the VNC client.
When you are done, you will need to run
vncserver -kill :1
(Replace the 1 with the display number you got.)