How to make use of these coordinates?Follow

Hi,

I wonder how I' am supposed to use all these coordinates given on this board..
Like.. I want to know where to find Hillshire Ruins, okay..



Okay.. So S27.8, W58.7 - But how am I supposed to make use of that?
There is no coordinates on my World Map in-game, so what does these coordinates tell me? How to use them?

Thanks