In order to get this, you cannot skip any of the puzzles in the game. If you do, you will need to restart (or at least back up before the puzzle you skipped.
Here's a pretty definitive guide for if you get stuck. The author is the same one who wrote the guide for the last one. Just don't let it ruin the game for you. http://www.gameboomers.com/wtcheats/pcSs/SH6/SH6.htm