Now for the wiring...
There can be variations on this but the idea is to take the two wires coming from the wall switch and make some changes to one of them in the ceiling box. Originally one of the wires was attached to the hot or source wire, usually using a wire nut. You want to separate these two and put both in the two "source" connectors on the switch. The other wire coming from the wall switch has to be connected to the "control" terminal. Remember that the XPS3 has two connections for each terminal type on the switch.
The two wires coming from the fixture are easy. One goes to "load" and the other goes to "neutral" on the switch. If you want to get fancy, use a continuity tester to find out which wire is attached to the outer ring on the lamp sockets and connect that one to neutral.
The other "neutral" terminal is for the neutral wire coming out of the ceiling.
The last thing to do is to install the WS14/XPSS in the wall box in the usual manner and you are done.
I hope this info was useful. Have fun upgrading for CFL's.