Within the grid you must enter every letter from A to Y. Each letter is next to the previous letter either horizontally, vertically or diagonally. The clues around the edge tell you which column, row or diagonal each letter is in.
IF you get REALLY stuck, you can type "help" into the answer box to reveal the letter, however this only works for the four corners or the centre.
Also, your answer must correspond to the yellow box. Use either "Tab" or click to move the yellow box.