i purchased on steam but i have a guess that you
might find it available in your
TGC account's Product list similar to how Studio's Bonus Tutorials is available at the same place. it's worth a look.
also, make sure that you don't already have it by selecting DLC from the IDE toolbar. there it's called "Instructors Guide". maybe the TGC version automatically downloads/installs it.
(i hope this is the same DLC):