For anyone wondering who doesn't already have it, here's how you put the WCG stats into your Free-DC signature. (This is the larger number of the 2...the one that is displayed on your "My Grid" page.)
In the WCG line in the Free-DC statstool enter NameXtremeSystems.
For example mine is mcflurry4321XtremeSystems
I know lots of you have figured this out, but if you haven't...here you go :)
This is also assuming you know how to work with the Free-DC statstool. Ask if you have anymore questions.