In order to sink a ship you must locate the cells which it occupies and hit all these cells. You indentify a cell by typing in its x-y coordinates. The x coordinate indicates how many cells to the right (starting from the left edge of the cell area) you wish to select and the y coordinate indcates how many cells from the top you wish to select. So, if you enter 6 16 you will select the cell six over from the left and 16 down from the top.