Hellow, how can I show all the grid at the start? Thank you in advance,

In the documentation for the map, under the title Mapping everywhere, is a method that will calculate the map coordinates of every room.

In that code snippet is a line: Grid_DrawRoom (room, false, game.pov) which is commented out. Remove the // from that line and it will draw the rooms on the grid as well as calculating where it should go.