To log-in to a different computer within Swansea Physics, you should use the unix/linux command ssh. The syntax from a unix machine is:
ssh username@pc_name.swan.ac.uk
If you are unfortunate enough to be using a Windows machine, then you can obtain a good ssh client from:
http://www.chiark.greenend.org.uk/~sgtatham/putty/
Note: you cannot directly access Theory Group machines from outside the Swansea Physics Department. See for how to do this.