You should now be in your room, and wherever in the room you put your particle system, you should see a small white circle.  Now, open the console with the ~ key.  If you've forgotten the name of your particle system, you can always type "listps" in the console, and it will list all of the particle systems in the map.  Most of these are not user entered, and you should not try and edit them.  When you've found the name of the particle system you want to edit, type "editps [particle system name]"  which in our case would be "editps test".  Now, simply press the F4 key, and we're set to start editing the particle systems.  You should see 11 bars on the screen, and you should also see your mouse pointer.  You should also still be able to move your character around using the standard a, w, s, d and arrow keys.