The entrypoint for the puzzle area is at 5961, 1013, 2857. Pull the lever to get in.
The puzzle is timed, so choose quickly during the early part of the game.
The Tarken Glacier puzzle is a game of Dots and Boxes! Also known as Sticks or Dots-Squares or tons of other names. The aim of the game is to makes boxes (squares) out of lines while not letting the other player (Computer in this case) gain boxes.