This achievement requires that you finish the Knight's Tour chess puzzle without making any mistakes. This puzzle is located in the back right corner of Amaro's secret room behind the waterfall. You must collect the knight chess piece from the safe, and then activate the puzzle. There are three rounds to the puzzle, with each round longer and trickier than the last. You must always move you piece in the "L" pattern as a knight would, and you can't move to the same space twice. See the link below for the solution you should follow for all three rounds.
Knight's Tour Chess Puzzle Solution