This may have already been asked, but I'm not quite in the mood to scroll through 62 pages of Q&A.
I'm running 1.3, and I added the unzipped folder to my "Kerbal Space Program" folder. I opened the game, and tried Alt+H, but it didn't seem to be doing anything. I didn't notice an "H", so I'm not sure whether it was there or not. Anyways, I then manually moved the "Kerbdata" folder into the "Gamedata" folder alongside "Squad". I can now see the "H", but when I click it or do Alt+H, it doesn't do anything. I have tried this in the Space Center view, The VAB view, and when flying an actual vessel, all three of which times neither action seemed to trigger anything. Thanks! -Super