As you can see i am not very good at explaining things but crawler has it down to a T, but remember, when building these units, all you got to do is open the build window on the
SPECIAL EDITION UNIT .
The image shows i want to build SU TANK,but dont click build until you change code in CE, once you have build all units refresh and njoy.
This is the way i done it but like crawler said, a few other ways exist.