Hi POD,
If you are using Steam then it should have downloaded already, I have just set up a new Desktop and re-installed SSE from Steam.....the Ferry Pack was automatically downloaded and I was prompted to type in the Key. I was subsequently hit by the "customCommand.DLL" issue but eventually figured out the solution by trawling through posts here.....thanks to all.
Hoping for a better experience this time, got a bit fed up last time I starting using SSE again, will try to be a bit more patient this time :-)
good luck,
Andy