You get two numbers from the books on the shelves on the left. When you run your cursor over the map two numbers show up and they change as you move your cursor over the map. You have to place your cursor on the place on the map that matches the numbers you have been given. For example if your numbers are;
-63,66N Then that combination would be in the upper left of the map,or if you have
60,108S that combination would be in the lower right on the map.
When your cursor gets on the right spot then you click your mouse.