When using "graphics programs" (e.g., Emacs, gnuplot & GrADS) in Linux/Unix computers over the network, a so-called X-connection is needed. Otherwise, you won't get your graphical windows opened.
ssh -X computername e.g: ssh -X numlab.fmi.fi
[ NB: The previous description is valid for the Physicum computer classes. If you use your own PC, and don't have Xming or something similar available, you need to find and install the program, for example from here].
Having started XSession, take a Putty connection to the linux computer in which you will be working, e.g. eddy.atm.helsinki.fi. Write the computer name to the Host Name box and then use the mouse to click on SSH and X11 on the left. Insert a cross to the box Enable X11 forwarding. Finally, push the Open button.